A card that shows less capacity after formatting is alarming, but it is often a partition problem, not a shrinking card. Formatting only rewrites the file system inside a partition. It does not change the partition size. If the partition was created smaller than the card, or if part of the card is left unallocated, Windows will report only the partition size, and the rest will look missing. A second possibility is simpler: advertised capacity and Windows capacity are measured differently, so a 128GB card never shows as a full 128GB in Windows. A third possibility is serious: a counterfeit card that reports more space than it physically has.

Fix in order

1. Check the real numbers first. Open Disk Management with Windows + X and find the card by its total disk size. Note the size of each partition and any unallocated space. If the disk total looks right but one partition is small, the missing space is almost certainly unallocated space, not lost hardware.
2. Do not panic about a small shortfall. Drive makers count a gigabyte as 1,000,000,000 bytes, while Windows counts it as 1,073,741,824 bytes. That alone makes a nominally 128GB card show around 119GB. File system overhead takes a little more. A shortfall of roughly that scale is normal and is not a fault to fix.
3. Reclaim unallocated space. If Disk Management shows unallocated space beside a small partition, you can extend the partition into it, or delete the small volume and create a new volume using the full space. Only delete a volume if you have backed up its contents, because deletion erases it. Then format the new, full-size volume to FAT32 with guiformat, checking the drive letter first.
4. Restore full capacity from scratch. If the layout is messy, with several small partitions or a leftover partition from another device, the cleanest route is: in Disk Management, delete the volumes on that card only, create one new simple volume using all available space, then format it to FAT32. Verify the disk size at every step, so you do not delete a volume on a different drive.
5. Check for a second partition. Some cards arrive with a small hidden or recovery partition. That partition takes space and can confuse capacity readings. Do not delete a partition you do not understand on a drive you still need, but on a blank card you intend to reuse, a single full-size partition is usually what you want.
6. Test for a fake card if the numbers do not add up. If a card claims 512GB but consistently fails after writing far less, or files vanish after you copy them, run a write-and-verify test with a free tool such as h2testw. It writes test data across the card and verifies it, which takes a long time on a large card. Run it only on an empty card, because it fills the card with test files, and delete those test files afterwards.

Why cluster size is not the usual culprit

Cluster size affects wasted space, not reported capacity in the way expected. A large cluster size means small files waste more space inside their clusters, so a card full of tiny files will hold fewer of them. It does not normally make a 128GB card report as 32GB. If your card reports a smaller size, look at partitions and unallocated space first, then counterfeit-card signs. Changing cluster size alone will not restore that space.

The 4GB single-file limit also does not reduce total capacity. If you cannot copy a large video, the problem is the file size, not missing capacity: split the file, or use a file system the device supports.

Fake and counterfeit card warning signs

A counterfeit card is programmed to report a larger capacity than it has. Early use looks normal, because files are written to real space first. Once writing passes that real capacity, new files overwrite old ones or vanish. Signs include a price far below normal, an unknown seller, and files that become unreadable once the card is nearly full. A write-and-verify test checks what can be read back, not what the card claims.

If a test proves the card is fake, do not keep using it for important files. No format or partition trick creates physical storage that is not there. Keep proof of purchase, contact the seller, and replace the card from a trusted seller.

What NOT to do

• Do not delete volumes on a disk you have not identified by size. Disk Management lists every drive, and deleting the wrong one erases the wrong data.
• Do not run a write-and-verify test on a card with files you need. The test fills the card, so back up first or use an empty card.
• Do not assume a format will fix a fake card. Formatting rewrites the file system; it does not add storage.
• Do not keep copying files onto a card that loses data after a certain point. Stop, test it, and replace it if it fails.

If this did not work

If Disk Management shows the full disk size but no partition tool can create a full-size volume, try another reader and another PC. A faulty reader can misreport size, and a second reader quickly separates a reader problem from a card problem. If the card shows a far smaller total on every reader and PC, and a verify test fails, treat it as damaged or counterfeit and replace it.

If the card shows the right size after you recreate the volume but your device still reports less, check the device manual for a maximum supported capacity. Some older devices only address part of a large card. In that case the PC is correct and the device is the limit, and a smaller card that the device fully supports is the practical answer.

This site is unofficial and unaffiliated with RidgeCrop and Microsoft. Guiformat is Windows-only and formats an existing partition; it does not create or resize partitions, so the Disk Management step above comes first when space is unallocated.

FAQ

Why does my 64GB card show about 59GB? That is mostly the difference between how makers count gigabytes and how Windows counts them, plus file system overhead. It is normal, not missing space.

Will reformatting to FAT32 restore the missing space? Only if the partition itself was too small and you recreate a full-size partition first. Reformatting the same small partition will give you the same small size again.

How long does a write-and-verify test take? A long time on a large card, because it writes and then reads back the whole capacity. Start it when you do not need the card, and leave the reader undisturbed.

Is my card fake if it shows less than advertised? Not necessarily. A small shortfall is normal. A card is suspect when it claims a large size but fails a full verify test, or loses files once it passes a much smaller amount of written data.

Related fixes

• Drive missing from the guiformat dropdown
• Volume too large and cluster errors
• Format stuck or not responding
• How to format an SD card to FAT32
• Get FAT32 GUI Formatter

There are two different problems behind the words still exFAT. The first is that the format did not actually change the volume you are looking at: Windows still reports exFAT, which means the FAT32 format either went to a different volume, failed silently, or was never applied to this partition. The second is that the format did succeed to FAT32, but the device still will not read the card. Those need different fixes, so verify the file system on the PC before you blame the device, and verify the device requirements before you reformat again.

Fix in order

1. Verify the file system properly. In File Explorer, right-click the drive, choose Properties, and read the File system line. Do not rely on memory or on what a format tool said last time. Also open Disk Management and check the same volume by size and letter. If both still say exFAT, the FAT32 format did not take effect on this volume.
2. Check whether you formatted the wrong drive. Drive letters can change when you swap readers or ports, and a card can have more than one partition. If you formatted a small partition or a different USB drive, the card you are holding may be unchanged. Match the volume by size in Disk Management, not by letter alone.
3. Reinsert the card and refresh. Remove the card safely if Windows allows it, reinsert it, and check Properties again. A stale Explorer view can occasionally show old information until the volume is remounted. Restarting the PC is a stronger version of the same check if reinsertion does not refresh it.
4. Format again, carefully, as administrator. Run guiformat as administrator, select the verified drive, choose a cluster size, leave Quick Format ticked, and click Start. Watch for an error or a completion message, and do not close the tool early. After it reports success, check Properties again before you put the card in the device.
5. Check the device manual. If Windows now says FAT32 but the device still will not read the card, look for the device maximum card capacity, supported file systems, and any required cluster size or partition layout. Some devices expect a single partition, some only support cards up to a stated size, and some need a specific folder structure that formatting alone does not create.
6. Test the card in another device or PC. If a second device reads the FAT32 card, the first device requirements are the problem, not the format. If no device reads it, and Windows also struggles with it, the card, reader, or partition layout is more likely at fault.

Common traps after a successful FAT32 format

The 4GB single-file limit is the most common trap. FAT32 cannot hold a single file larger than 4GB, no matter how large the card is. If you copy a video, disk image, or game file over 4GB onto a FAT32 card, the copy will fail, and some devices may report the card as unusable or full when the real problem is one oversized file. Split the file if the device supports split files, or use a file system the device supports for large files, if it supports one.

Cluster size is a subtler trap. Most devices accept the common default, commonly 32KB, but a few older or specialised devices are picky. If a device manual specifies a cluster size, follow it. If it does not, do not change cluster size at random: a wrong guess can make a working card unreadable on that device, and you will have to format again.

Partition layout is another trap. A card with several partitions, or with a partition that does not start where the device expects, may be ignored by a camera, console, or media player even though Windows reads it fine. For device use, a single partition using the full card, formatted to FAT32, is the safest layout unless the manual says otherwise.

What NOT to do

• Do not keep reformatting the same card with different cluster sizes without checking Properties and the manual. Repeated formats do not fix a device capacity limit.
• Do not format a second drive hoping the first card will change. Always match the volume by size in Disk Management before you click Start.
• Do not copy a file over 4GB and conclude the card is broken when the copy fails. That failure is a FAT32 limit, and it will happen on any correctly formatted FAT32 card.
• Do not use a card in a device that states a lower maximum capacity and expect a PC format to override that limit. The device limit is separate from the PC format.

If this did not work

If Windows still says exFAT after a careful, administrator format with the correct letter, check Disk Management for a second partition on the same card. You may be checking one partition while guiformat formatted another. Delete only card volumes you understand, create a single full-size volume, format that volume to FAT32, and verify Properties again.

If Windows says FAT32, the card works on a PC, but the target device still refuses it, try a smaller card that is within the device stated maximum, if you have one. If the smaller card works, the original card exceeded a device limit, not a format problem. If no card works in that device, check the device slot, firmware, and manual before you format more cards.

This site is unofficial and unaffiliated with RidgeCrop and Microsoft. Guiformat is Windows-only, formats an existing partition to FAT32, and does not create or resize partitions. Newer Windows 11 builds raise the command-line FAT32 limit to 2TB, while the graphical tool still stops at 32GB on many systems, but that PC limit is not the same as a device limit.

FAQ

How do I know the format actually worked? Right-click the drive in File Explorer, choose Properties, and read the File system line. It should say FAT32. Cross-check the same volume by size in Disk Management.

Why does my device still say the card needs formatting? The device may not support the card capacity, cluster size, or partition layout, or it may expect a folder structure that formatting does not create. Check the manual, and test the card in another device.

Can FAT32 hold a 5GB video? No. The single-file limit is 4GB. Split the file, if the device supports split files, or use a file system the device supports for large files.

Should I format to exFAT instead? Only if the device supports exFAT and you need files over 4GB. If the device requires FAT32, exFAT will not help, even if Windows formats it easily.

Related fixes

• Drive missing from the guiformat dropdown
• Format stuck or not responding
• Volume too large and cluster errors
• How to format an SD card to FAT32
• Get FAT32 GUI Formatter

Write protection means Windows will let you read the card but will refuse to write to it, and guiformat cannot format a volume it cannot write to. The good news is that the most common cause is physical and takes seconds to fix. The less good news is that write protection can also come from a failing card, a faulty adapter, or a policy on the PC, and those need different handling. Work through the physical checks first, because they fix most cases without touching any system setting.

Fix in order

1. Check the lock switch on a full-size SD card. Full-size SD cards have a small sliding switch on the side. If it is in the Lock position, the card is read-only. Slide it fully to the unlocked position, reinsert the card, and try again. A switch that sits halfway, or that moves too easily, can also cause intermittent protection.
2. Check the adapter, not just the card. MicroSD cards have no lock switch of their own. The switch is on the microSD-to-SD adapter. If you are using an adapter, the adapter switch is the one that matters. Try a different adapter, because adapter switches wear out and can report Lock even when they look unlocked.
3. Try another reader and another PC. If the card is writable in another reader or on another PC, the first reader, adapter, or PC setting is the problem. If it is write-protected everywhere, the card or adapter is more likely at fault.
4. Check whether files can be changed at all. Try renaming a file, or creating a small test file, on the card from File Explorer, on a copy you do not need. If every write fails with a protection message, the protection is real and system-wide for that card. If only guiformat fails, check the drive letter, run guiformat as administrator, and check for a lock from another program.
5. Check for a read-only volume in Disk Management. Open Disk Management with Windows + X and look at the card volume. A volume that shows as read-only, or a disk that shows as offline or read-only, needs a different fix from a simple lock switch. Note exactly what Disk Management says before you change anything.
6. Check, do not hack, registry and policy settings. On some PCs, a registry value or a group policy can force removable drives to be read-only. This is a check for experienced users only, and only on a PC you own. Back up the registry before you look at or change any registry value, and do not change a setting on a work or school PC: ask your IT team instead, because the policy may be intentional. If you are not comfortable backing up the registry and restoring it, stop at this step and use another PC or another card.
7. Consider a failing card. Flash cards can enter a read-only state when they fail, as a last effort to preserve readable data. If the card became write-protected suddenly, shows read errors, or loses files, copy everything you can read to another drive immediately, while reading still works. Do not keep trying to format a failing card in the hope it will recover.

Adapter versus card: how to tell

That one-variable-at-a-time approach matters, because a lock switch, a reader, a policy, and a failing card can all produce the same message. Changing the adapter is cheap and fast, so do it before you consider system settings. Changing a registry value is slow, risky, and pointless if the adapter was the problem all along.

What NOT to do

• Do not tape over the lock switch or force it as a permanent fix. A switch that will not stay unlocked is a sign to replace the adapter, not to improvise a repair that can fail mid-format.
• Do not edit the registry without a backup, and do not follow a registry edit presented as safe for beginners. A wrong registry change can affect more than one drive.
• Do not change group policy on a work or school PC. If the policy is managed, it is there for a reason, and your IT team is the right contact.
• Do not disable security software permanently to fix write protection. Security software does not normally make a card read-only, and leaving it off creates a larger problem than the one you are fixing.
• Do not keep formatting a card that has entered read-only failure mode. Copy readable files first, then replace the card.

If this did not work

If the switch is unlocked, a second adapter and a second PC both report protection, and the card shows no other fault, check whether the PC you own has a removable-drive policy set, with a registry backup in place and a clear note of what you changed, so you can undo it. If you are not comfortable doing that, use a different PC that does not enforce the policy, or replace the card and adapter together, since a worn adapter switch is still the most likely hardware cause.

If the card is readable but permanently write-protected, and a second card works in the same reader, treat the first card as failed. Copy what you can, then replace it. A card that cannot be written to cannot be formatted to FAT32, and no cluster size or format tool changes that physical or firmware state.

This site is unofficial and unaffiliated with RidgeCrop and Microsoft. Guiformat is Windows-only, formats an existing partition to FAT32, and does not create or resize partitions. It also cannot override a genuine hardware lock or a failing card.

FAQ

Does a microSD card have a lock switch? No. The switch is on the full-size SD adapter you put the microSD card into. Check the adapter switch, and try a different adapter.

Why is the card write-protected on one PC but not another? The first PC may have a policy or reader problem, or the adapter fit may differ between readers. Test the same card and adapter on a second PC to separate a PC problem from a card problem.

Is it safe to change a registry value to remove protection? Only for experienced users, only on a PC you own, and only with a registry backup first. If you are unsure, do not change it, and ask for help or use another PC.

Can guiformat force a format on a locked card? No. If Windows cannot write to the volume, guiformat cannot format it. Fix the lock, adapter, policy, or failing card first.

Related fixes

• Drive missing from the guiformat dropdown
• Format stuck or not responding
• Card shows less capacity after formatting
• How to format an SD card to FAT32
• Get FAT32 GUI Formatter

Two different messages get confused here, and they need different fixes. The first is a Windows limit: the built-in graphical format tool in File Explorer and Disk Management will not offer FAT32 for volumes over 32GB. The second is a FAT32 rule about clusters: a FAT32 volume must contain enough clusters to be a valid FAT32 volume, and if your cluster size is too large for a small volume, the cluster count falls below that minimum. Guiformat exists largely to get past the first problem, but it cannot break the second rule, so choosing the wrong cluster size can still stop it.

What a cluster is, in one paragraph

A cluster, also called an allocation unit, is the smallest block of space the file system hands out to a file. If the cluster size is 32KB, even a 1KB file occupies a full 32KB cluster, and the rest of that cluster is wasted for that file. Larger clusters mean fewer clusters overall, less bookkeeping, and more wasted space on small files. Smaller clusters mean more clusters, more bookkeeping, and less wasted space. The total number of clusters is roughly the volume size divided by the cluster size, and FAT32 needs that number to be large enough.

Microsoft documentation describes the FAT32 minimum as at least 65,527 clusters; guiformat messages are often phrased around 65,536 clusters, about 64K clusters. Either way, if the cluster size is so large that the volume would contain fewer clusters than the minimum, the format is not valid, and the tool should refuse it.

Fix in order

1. Read the exact message. If the message says the volume is too large, you are hitting a tool or Windows limit. If it mentions clusters, you are hitting the cluster-count rule. Do not apply the cluster fix to a size-limit problem, or vice versa.
2. For a cluster-count error, choose a smaller cluster size. In guiformat, open the Allocation unit size dropdown and step down one size: for example, from 64KB to 32KB, or from 32KB to 16KB. A smaller cluster size increases the cluster count for the same volume. Try again after each step down.
3. For a small volume, do not start large. A small card or partition with a large cluster size is the classic trigger. A 2GB volume at 32KB clusters gives roughly 65,536 clusters, right at the edge. At 64KB it would give roughly half that, which is too few. Start at 32KB or smaller for small volumes, unless the target device manual asks for a specific size.
4. For a large volume, do not go too small without a reason. Very small clusters on a very large volume create a huge number of clusters and a larger file allocation table. The default allocation unit in guiformat is commonly 32KB, and for most SD cards and USB drives that is a sensible starting point. Change it only to fix an error or to meet a device requirement.
5. Check the volume size itself. FAT32 has a single-file limit of 4GB, always. The volume limit depends on sector size: up to 2TB on 512-byte-sector drives, and up to 16TB on 4K-sector drives, as set out for this site. If your volume is beyond what your device or your version of Windows can handle, splitting it into a smaller partition, or choosing exFAT for a device that supports it, may be the honest answer, not a larger cluster size.
6. Recheck the drive letter and try a quick format. After changing the cluster size, verify the drive letter again, leave Quick Format ticked if you want a fast result, and click Start. A quick format usually finishes in seconds. A full format does not, and it will not fix a cluster-count error.

Worked examples

These are rounded illustrations, not exact counts, because usable space is slightly less than advertised size. The direction matters: smaller clusters raise the count, larger clusters lower it.

Volume too large: which limit are you hitting?

Windows Explorer and Disk Management historically would not offer FAT32 above 32GB: a Windows graphical tool limit, not a FAT32 limit. Newer Windows 11 builds raise the command-line FAT32 limit to 2TB, while the graphical tool still stops at 32GB on many systems. The command line supports a quick format, such as format E: /FS:FAT32 /Q, where E: is your drive letter. Without /Q, a full format is slow.

Guiformat can format larger volumes graphically, without the 32GB graphical limit. But a large volume is not automatically right for your device: check its manual for a maximum capacity and cluster size, because a PC format can still fail on the device.

Clusters cannot be 64KB or larger for FAT32 in the Microsoft limits, because some programs calculate disk space incorrectly with larger clusters. The fix for a cluster-count error is down, and the fix for a too-large volume is a different tool, a smaller partition, or a file system your device supports.

What NOT to do

• Do not choose the largest cluster size hoping for speed. On a small volume it triggers the cluster error, and on any volume it wastes space on small files.
• Do not choose the smallest cluster size by default for a huge volume. It increases bookkeeping and can slow some operations, with no benefit unless a device asks for it.
• Do not split a card into many partitions to dodge a limit unless your device supports that layout. Many cameras, consoles, and media players expect a single partition.
• Do not ignore the 4GB single-file limit. No cluster size changes it. A file over 4GB will not fit on FAT32, however you format the volume.

If this did not work

If stepping the cluster size down to the smallest sensible option still gives a cluster error, check the partition size in Disk Management. You may be trying to format a tiny partition, a leftover recovery partition, or the wrong volume entirely. Confirm the size matches the card you intend to format. If the partition is below roughly 32MB, it may be too small for a valid FAT32 volume.

If the error is about volume size, verify the volume in Disk Management, try the Windows command-line format with /Q if your Windows version supports the size, and respect any lower maximum in the device manual.

This site is unofficial and unaffiliated with RidgeCrop and Microsoft. Guiformat is Windows-only and formats an existing partition; it does not create or resize partitions.

FAQ

What cluster size should I pick? Start with the default, commonly 32KB, unless a device manual specifies a size. If you hit a cluster-count error, step down.

Does a larger cluster size make the card faster? Not enough to justify breaking the cluster rule. Larger clusters waste space on small files and can trigger the minimum-cluster error on small volumes.

Why does Windows say FAT32 is unavailable over 32GB? That is the graphical tool limit, not a FAT32 limit. Newer Windows 11 command-line builds allow up to 2TB.

Can I format a 1TB drive to FAT32? FAT32 allows large volumes within the sector-size limits above, but your device may not. Check its maximum capacity first.

Related fixes

• Failed to open device, GetLastError() = 32
• Drive missing from the guiformat dropdown
• Card shows less capacity after formatting
• How to format an SD card to FAT32
• Get FAT32 GUI Formatter

When you double-click guiformat.exe, Windows may show a blue screen headed Windows protected your PC, saying it prevented an unrecognised app from starting. That screen does not, by itself, mean the file is malicious. It means Microsoft Defender SmartScreen does not recognise the app: it is unsigned, or it has not built up the reputation SmartScreen uses to trust a file. Guiformat is a small, older, unsigned portable tool from the 2013 era, so it is exactly the kind of file SmartScreen is designed to pause on, even when the user deliberately downloaded it.

SmartScreen checks reputation and signing, not whether you wanted the file. An unsigned file has no verified publisher for Windows to display, so Windows cannot tell you who made it from the signature alone. A file that is rarely downloaded, or downloaded from a mirror rather than a single well-known source, also has less reputation data. Both factors together explain why a legitimate, long-used utility can still trigger the warning, and why a warning should make you check the file carefully rather than click through automatically.

Fix in order

1. Stop and check where the file came from. Only continue if you downloaded guiformat from a source you intended to use, and you recognise the file name, guiformat.exe. If the file arrived by email, from a pop-up, or from a site you did not intend to visit, do not run it. Delete it and get it from the intended source instead.
2. Check the hash before you run it. Open PowerShell, run Get-FileHash with the full path to the file, for example Get-FileHash C:\Users\YourName\Downloads\guiformat.exe -Algorithm SHA256, and compare the result with the hash printed on our download page. The hash printed on our download page is 647fb4f5108af632c3d52fec34934922c50c70585697504e92fb80b3b7d05ee3. Compare it only as the hash printed on our download page; compare after downloading, and do not treat a match as proof of anything beyond that match.
3. Understand what a hash match does and does not prove. A match shows your downloaded file is identical to the file that hash describes, and that it was not damaged or swapped during that download. It does not prove the original file is safe, and it does not prove a developer published it, especially because our download is a third-party mirror, not the developer site, and its hash could not be independently verified in October 2026. If the hash does not match, do not run the file. Delete it and download again.
4. Use More info, then Run anyway, only for this file. On the SmartScreen screen, click More info. Read the app name and publisher shown there: for an unsigned file, publisher will be unknown. If the name matches guiformat and you have completed the source and hash checks above, click Run anyway. This allows this one run; it does not turn SmartScreen off.
5. Run guiformat as administrator for the format itself. After SmartScreen allows the file, right-click guiformat.exe and choose Run as administrator for the actual format, and verify the drive letter before you click Start.

What the SmartScreen screen is telling you

What NOT to do

• Do not disable SmartScreen permanently, and do not disable Microsoft Defender permanently, to run one tool. The safe route is to allow one file you have checked, while protection stays on for everything else.
• Do not click Run anyway on a file you did not intend to download, or on a file whose hash does not match. A warning plus a mismatched hash is a stop signal, not a hurdle.
• Do not add a permanent exclusion for a file you have not checked. An exclusion tells security software to stop checking that file in future, which is a larger decision than a single run.
• Do not download guiformat from a random mirror because the first download triggered SmartScreen. SmartScreen will trigger on the same unsigned file from another mirror too, and a new mirror adds a new source to check.

There is a related, safer option for a single downloaded file: right-click the file, choose Properties, and, if an Unblock box appears on the General tab, tick it and click OK. That removes the downloaded-file mark for that one file, while SmartScreen stays on for everything else. Only use it for a file you have already checked by source and hash.

If this did not work

If there is no Run anyway button, do not try to work around SmartScreen. The file may be known to be harmful, or your organisation may block it. Delete the file, and on a work or school PC, ask your IT team. If SmartScreen appears in your browser instead, as a warning about a download or a website, treat that as a separate warning: only keep a download if you trust the source and the hash check passes.

If you run guiformat successfully but then hit a format error, the SmartScreen step is finished and the problem has moved on. A lock error, a missing drive, or a frozen format each have their own fixes, and repeating the SmartScreen steps will not fix them. Check the drive letter, run as administrator, and work through the error message itself.

This site is unofficial and unaffiliated with RidgeCrop and Microsoft. Guiformat is Windows-only, it does not install anything, and it formats an existing partition to FAT32. Do not claim any safety badge for our download: it is a third-party mirror, and the hash above is only the hash printed on our download page.

FAQ

Does SmartScreen mean guiformat is a virus? No, not by itself. It means SmartScreen does not recognise the unsigned file. Check the source and hash, and only continue if both checks pass and you intended to download it.

Why does an old tool trigger SmartScreen? Because it is unsigned and does not carry a verified publisher, so Windows cannot confirm who made it from a signature, and it has limited reputation data compared with a signed, widely downloaded app.

Will I see the warning every time? You may see it again if you run the file from a different location or download a fresh copy, because allowing one run does not permanently trust every copy. That is normal, and it is not a reason to turn SmartScreen off.

What if the hash does not match? Do not run the file. Delete it, download again from the intended source, and check again. A mismatch means the file is not the file described by the printed hash.

Related fixes

• Failed to open device, GetLastError() = 32
• Drive missing from the guiformat dropdown
• How to format an SD card to FAT32
• Get FAT32 GUI Formatter

A frozen format is not always a failed format. A quick format usually finishes in seconds, but a full format writes across the whole volume and can take a long time on a large card, especially through a slow reader. Windows may also report guiformat as not responding while it waits for a slow card or reader, even though work is still happening in the background. The first job is therefore to tell a slow format from a stuck one, and the second is to avoid making it worse by pulling the card out at the wrong moment.

Fix in order

1. Wait, and watch for signs of life. For a quick format, a minute or two with no progress is suspicious. For a full format on a large volume, allow much longer, and watch the reader light, if it has one. Flickering activity suggests work is still happening. No light, no progress, and no disk activity for a long stretch suggests a stall.
2. Do not unplug the card mid-format if you can avoid it. Removing a card during a write can leave the partition layout half-written. That does not usually destroy the card permanently, but it can make the next attempt harder and may require you to delete and recreate the volume.
3. Close guiformat only after a fair wait. If progress has truly stopped and the window will not respond, close it through Task Manager if needed. Then check Disk Management: the volume may show as RAW, unformatted, or with a partial layout. That is expected after an interrupted format, not proof the card is dead.
4. Reseat the card and change the reader or port. A loose connection is a common cause of a freeze. Reinsert the card firmly, try a port directly on the PC rather than through a hub, and try a different reader. Then open guiformat as administrator and check the drive letter again.
5. Retry with a quick format first. Select the correct drive, leave Quick Format ticked, and try again. If a quick format succeeds, the earlier freeze may have been a connection or layout problem rather than a dying card. Verify the result in File Explorer properties before you trust it.
6. Delete the volume and recreate it as exFAT, then retry guiformat. If guiformat still freezes on the same volume, open Disk Management, delete the volume on that card only, and create a new simple volume formatted as exFAT. Once that succeeds, run guiformat as administrator and format the new volume to FAT32. A clean layout often clears the corrupt or half-written structure that was stalling the format.
7. Try a different card in the same reader. If the second card formats quickly and cleanly, the first card is the more likely problem. If both cards freeze in the same reader, the reader or port is more likely at fault.

Why a format freezes

The most common causes are connection, layout, and media. A reader that loses contact for a moment can stall a write, and Windows may wait a long time before it admits the device is gone. A corrupt partition layout, left by an interrupted format or by another device, can also stall a format tool that expects a clean starting point. That is why deleting and recreating the volume helps: it replaces the questionable layout with a fresh one.

Failing media is the more serious cause. A card with bad areas can hang when a format reaches them, and a full format is more likely to hit one than a quick format. Repeated freezes, read errors, disappearing drives, and corrupt files are warning signs: do not trust such a card with files you cannot afford to lose.

Quick format versus full format

A quick format rewrites file system structures but does not overwrite every sector, so it usually finishes in seconds. A full format works across the volume and takes far longer. So a quick format hanging for ten minutes is a problem, while a full format on a large, slow card may simply be slow. Use a quick format unless you need a full one.

Do not choose a full format as a repair tool for a failing card. It cannot repair worn flash memory, and it erases data more thoroughly, making later recovery harder. Copy needed files first, while the card still reads.

What NOT to do

• Do not repeatedly force-close and restart a format on the same volume without changing anything. If the layout is the problem, the same attempt will stall again.
• Do not pull the card out, reinsert it, and immediately click Start again without checking Disk Management. You may be formatting a half-written layout, or the wrong letter after reinsertion.
• Do not disable security software permanently to fix a freeze. A freeze is a connection, layout, or media problem, not a security setting to switch off.
• Do not trust a card that only formats after many attempts. Repeated stalls are data, not bad luck: treat the card as suspect.

If this did not work

If a clean volume, a different reader, and a different port all still freeze, and a second card works in the same setup, replace the first card. Continuing to format a failing card wastes time and risks data loss, because even a format that appears to finish may leave files unreadable later. If the data on the card matters, stop formatting attempts and copy what you can read to another drive first, or seek recovery help before you overwrite more of it.

If every card freezes in the same reader, replace the reader. If every card freezes on one PC but works on another, check that PC port and driver. Change one variable at a time.

This site is unofficial and unaffiliated with RidgeCrop and Microsoft. Guiformat is Windows-only, formats an existing partition to FAT32, and does not create or resize partitions.

FAQ

How long should I wait before calling it frozen? For a quick format, a few minutes with no progress or activity is enough to suspect a stall. For a full format, allow far longer, in proportion to the card size and reader speed, before you interrupt it.

Is it safe to close guiformat when it is not responding? It is safer than pulling the card out, but it can still leave a half-written layout. After closing it, check Disk Management, and be prepared to delete and recreate the volume before retrying.

Why does the card show as RAW after a freeze? An interrupted format can leave the file system incomplete, so Windows cannot recognise it. That is usually a layout problem, not permanent damage, and recreating the volume normally fixes it.

Should I try a full format to fix a freezing card? No. It is slower, more likely to hit bad areas, and erases data more thoroughly. Use a quick format, a clean volume, and a different reader first.

Related fixes

• Failed to open device, GetLastError() = 32
• Drive missing from the guiformat dropdown
• Card shows less capacity after formatting
• How to format an SD card to FAT32
• Get FAT32 GUI Formatter

If guiformat, also called FAT32 Format, shows Failed to open device with GetLastError() = 32 and the message The process cannot access the file because it is being used by another process, Windows is telling you something else is holding the drive open. Guiformat cannot get exclusive access while that lock is in place, so it stops before it changes anything. That is frustrating, but it is also useful: the error usually means the drive itself is still readable, and the problem is a lock, not a dead card.

What GetLastError() = 32 actually means

Error 32 is a Windows sharing violation. In plain language, another program has the drive, a folder on it, or a file on it open. Guiformat needs the whole volume to itself in order to rewrite the file system, so even one open handle can block it. The lock does not have to be obvious. You may have closed the visible window and still have a background process, a preview pane, or a sync tool touching the card.

The most common locks are easy to miss. File Explorer is the usual suspect: opening the card, previewing a photo, or leaving a folder window open can keep a handle on it. Antivirus scans, cloud sync, photo import, backup tools, and media players can do the same, as can any document opened from the card.

A second cause is permissions. If guiformat is not running with administrator rights, Windows may refuse the access it needs and report the same kind of failure. That is why running as administrator is part of the fix, not an optional extra. It does not, on its own, override a real lock from another program, so work through both parts in order.

Fix in order

Work from the gentlest fix to the strongest. Stop as soon as guiformat runs, and do not skip the drive-letter check at the end.

1. Close every Explorer window showing the card. Close any File Explorer window open on the drive, and close preview panes. If you opened a file from the card, close that program too, not just its window preview.
2. Close tools that may be watching the drive. Pause or close sync tools, photo importers, backup software, and media players that might be scanning the card. Wait a few seconds after closing them, because a scan does not always stop the instant the window closes.
3. Close guiformat, then reopen it as administrator. Right-click guiformat.exe and choose Run as administrator. Select the drive again from the dropdown, and check the letter against File Explorer or Disk Management before you continue.
4. Use Task Manager for a stubborn program. Press Ctrl + Shift + Esc, find the program that is using the card, select it, and choose End task. Only end programs you recognise. Do not end system processes at random.
5. Restart the computer. A restart clears locks left by programs that did not close cleanly. After the restart, do not open the card in Explorer first. Open guiformat as administrator and try again straight away.
6. Try another reader or port. If the error persists, remove the card safely if Windows allows it, then try a different card reader or a different USB port. A reader that works for reading can still behave differently when a format tool asks for exclusive access.
7. Try a Windows format first, then guiformat. Some users report that a quick Windows format to exFAT or NTFS, followed by guiformat to FAT32, clears the lock. Only do this if you have already backed up the card, because the Windows format also erases it. Then run guiformat as administrator and check the drive letter again.

One advanced last resort appears in user reports: ending Windows Explorer in Task Manager, running the format while Task Manager stays open, then restarting Explorer from Task Manager with File, Run new task, explorer.exe. Only try this if you are comfortable with Task Manager.

What NOT to do

• Do not force the format by disabling your antivirus permanently, or by turning off Windows security features. A temporary pause for a single, trusted scan is different from leaving protection off, and this guide does not recommend leaving it off.
• Do not pull the card out in the middle of a format. That can leave the partition layout half-written and make the next attempt harder.
• Do not keep clicking Start with different cluster sizes hoping the error will change. Cluster size does not fix a lock. Fix the lock first, then worry about cluster size if a different error appears.
• Do not end unfamiliar processes in Task Manager. Ending the wrong process can destabilise Windows and will not reliably free the drive.
• Do not assume the drive letter stayed the same after a restart or a reader change. Letters can move when you change ports or readers, so verify it every time.

How to tell which program is locking the drive

Start with what you can see: the taskbar and system tray for sync, backup, photo, and media programs, and any document or image opened from the card. If you recently inserted the card, wait a minute, because Windows may still be indexing it or a scan may still be finishing.

If this did not work

If you have closed programs, run guiformat as administrator, restarted, and tried another reader, and the error still appears, check the basics in Disk Management. Press Windows + X, open Disk Management, and confirm the card appears there with a drive letter and a partition. If it does not appear at all, the problem is detection, not a lock, and you need the missing-drive steps instead. If it appears but shows as unallocated, guiformat cannot format it yet, because guiformat formats an existing partition; it does not create one.

Also consider the card itself. Try a different card in the same reader: if the second card formats without error, the first card is the more likely problem. Copy what you can read first, while you still can.

This site is unofficial and unaffiliated with RidgeCrop and Microsoft. Guiformat is a Windows-only portable tool: it formats an existing partition to FAT32, it does not install anything, and there is no Mac or Linux version. If you are on another operating system, these Windows steps will not apply.

FAQ

Does GetLastError() = 32 mean my card is broken? Not by itself. It most often means another process is using the drive. A broken card is more likely if the card also fails to read, disappears repeatedly, or fails in a second reader with a second card working fine.

Will running as administrator fix it on its own? Sometimes, if permissions were the only problem. If another program holds the drive open, administrator rights alone will not release that lock. Close the program first, then run as administrator.

Should I disable my antivirus to format? No, not permanently, and this guide does not recommend it. Close or pause the specific scan only if you are sure that is the lock, and restore protection afterwards. If you are unsure, restart the PC and try before the scan starts again.

Is it safe to end Windows Explorer in Task Manager? It is a known workaround, but it removes your taskbar and desktop until you restart Explorer. Treat it as a last resort, keep Task Manager open, and restart Explorer immediately after the format.

Related fixes

• Drive missing from the guiformat dropdown
• Format stuck or not responding
• Volume too large and cluster errors
• How to format an SD card to FAT32
• Get FAT32 GUI Formatter

Warning: formatting erases everything on the selected volume. Back up any files you need first, and double-check the drive letter before you click Start. Formatting the wrong drive will erase the wrong files.

Guiformat only lists drives Windows can already see as a volume with a drive letter. If your SD card or USB drive does not appear in the dropdown, guiformat is not necessarily broken. In most cases Windows has not mounted the card, the reader or cable is at fault, or the card has no partition for guiformat to format. The fix is to work backwards: prove Windows sees the hardware, then prove Windows sees a partition, and only then open guiformat.

That last point matters more than it sounds. Guiformat formats an existing partition or volume to FAT32. It does not create a partition, resize a partition, or turn unallocated space into a usable drive. If Disk Management shows the card as unallocated, or as a disk with no volume, guiformat will have nothing to list, even if the hardware is perfect.

Fix in order

1. Reseat the card and the reader. Remove the card, check for dust or damage on the contacts, reinsert it firmly, and wait ten seconds. For a microSD card, check that it is fully seated in its adapter, and that the adapter itself is fully seated in the reader.
2. Try another port, then another reader. Move a USB reader to a port directly on the computer, not through an unpowered hub, if you can. Then try a different reader or adapter. Readers fail more often than cards, and a reader that reads one card slowly may fail to present another card at all.
3. Try another computer if you can. If the card appears on a second PC, the problem is with the first PC, its reader, or its drivers. If it appears nowhere, focus on the card, adapter, and reader.
4. Open Disk Management. Press Windows + X and choose Disk Management. Look for the disk by its size, not only by its letter. A card can be present as a disk even when it has no letter and therefore no entry in File Explorer or guiformat.
5. If the volume has no letter, assign one. In Disk Management, right-click the volume and choose Change Drive Letter and Paths, then Add and assign an available letter. Close and reopen guiformat, running it as administrator, and check whether the drive now appears.
6. If the space is unallocated, create a partition first. Right-click the unallocated space, choose New Simple Volume, and follow the wizard. You can format it as exFAT in this step; the point is to create a partition. Once the partition exists, guiformat should be able to list it and format it to FAT32. Check the drive letter again before formatting.
7. If Disk Management shows the disk as unknown or not initialised, stop and think. Initialising and creating a partition will erase what is on the card. Only continue if you have a backup or you accept that the data will be lost. If the data matters, copy what you can read first, or seek recovery help before you change the partition layout.
8. Use a partition tool if Disk Management is awkward. A partition tool such as EaseUS Partition Master can create a partition, assign a letter, and format a volume from one interface. Read every confirmation screen carefully, verify the disk size and letter, and do not apply a change to the wrong disk.

What each Disk Management result means

Reader, cable, and adapter checks that actually help

Start with the cheapest variables. A microSD-to-SD adapter is a common failure point: the adapter switch, contacts, and fit can all stop a good card from appearing. Try the card in a different adapter, and try a different card in the same adapter. If the second card appears and the first does not, the first card or its fit is the problem. If neither card appears, the adapter or reader is more likely at fault.

For USB readers, avoid long cables and unpowered hubs for this test, and plug the reader directly into the PC. Try a built-in laptop slot if one is available, as built-in slots and USB readers can behave differently with the same card.

Common mistakes

• Opening guiformat before checking Disk Management, and concluding the tool is broken when Windows has not mounted the drive.
• Choosing a disk by letter alone in Disk Management. Always match the disk size and, where possible, the label, because letters can change when you swap readers or ports.
• Formatting the wrong volume after assigning a letter. Assigning a letter can shift your attention, so recheck the letter in guiformat immediately before you click Start.
• Creating a partition over data you still need. A new partition does not preserve the old files. If the files matter, stop and copy or recover them first.
• Repeating the same reader and port and expecting a different result. Change one variable at a time, and note what changed.

If this did not work

If the card appears in Disk Management with a letter but still does not appear in guiformat, close guiformat completely and reopen it as administrator. Make sure no other format or partition tool is running, and make sure no Explorer window is open on the card. A lock can sometimes hide a drive from a format tool even when Windows itself can see it.

If the card appears nowhere, on no PC, in no reader, and in no adapter, it may have failed. Clean contacts gently with a dry, soft cloth, try once more, and test the reader with a known-good card before replacing anything.

This site is unofficial and unaffiliated with RidgeCrop and Microsoft. Guiformat is Windows-only, it does not install anything, and it cannot create a partition. If you need to create a partition first, Disk Management or a partition tool is the right step, and guiformat is the step after that.

FAQ

Why does File Explorer not show the card either? Usually for the same reason guiformat does not: the volume has no drive letter, or there is no partition. Fix the letter or partition in Disk Management first, and both programs should then see it.

Can guiformat format unallocated space? No. Guiformat formats an existing partition. Create a partition first, then format that partition to FAT32.

Should I initialise a disk that Disk Management calls unknown? Only if you do not need the data on it. Initialising prepares a new partition layout and can make old data harder to recover. If the data matters, get recovery advice before you initialise.

Does a different reader really make a difference? Yes. Readers vary in how they handle larger cards, adapters, and power. A second reader is one of the fastest ways to separate a reader problem from a card problem.

Related fixes

• Failed to open device, GetLastError() = 32
• Format stuck or not responding
• How to format an SD card to FAT32
• Get FAT32 GUI Formatter

Warning: formatting erases everything on the selected volume. Always double-check the drive letter before you click Start. This post is about what to do after that warning came too late.

Recovery after a format is possible in some cases, but it is not guaranteed, especially after a full format or new writes. A quick format rewrites file system structures but does not immediately overwrite every file sector, so recovery software may still find file data. A full format overwrites far more, and new files, a new format, or a new operating system install can overwrite what a quick format left behind. Be honest with yourself about which case you are in, because it changes what is reasonable to expect.

Fix in order

1. Stop immediately. Close programs that might write to the drive, do not copy files onto it, do not install software onto it, and do not run a second format to undo the first. If it is an external drive or card, remove it safely if Windows allows it, and set it aside until you are ready to attempt recovery.
2. Do not install recovery software onto the same drive. Recovery software itself is a write. Install it on your system drive or another drive, and recover files to a different drive, never back onto the formatted drive. Recovering to the same drive can overwrite files that have not been recovered yet.
3. Image or clone the drive first, if you can. If you have the space and a tool you trust, make a sector-by-sector image or clone of the formatted drive, and work from the image rather than the original. That way, a failed recovery attempt does not make the original worse. If imaging sounds unfamiliar, skip to the scan step rather than experimenting on the only copy.
4. Scan with recovery software. Recovery tools such as Disk Drill and EaseUS Data Recovery can scan a formatted volume and preview files they find. Start with a scan and preview: preview tells you whether the files you need are recognisable before you pay for recovery or save anything. Save recovered files to a different drive.
5. Check what was actually recovered, file by file. Open a few recovered files, not just their names and sizes. A file with the right name but corrupt contents is not a successful recovery. Check photos, documents, and videos you care about most first, while you still have the scan results.
6. Decide whether to keep trying or stop. If a scan finds nothing, or finds only corrupt fragments, further scans with different settings may help, but repeated writes to the same drive will not. If the data is irreplaceable and a scan fails, a professional recovery service is the next option, and it is also the option that should see the drive before you do anything else to it.

Quick format versus full format, honestly

Free scan and preview is a useful honesty check. Many tools let you scan and preview without paying, and charge for saving files. If the preview shows your files intact, saving is worth considering. If it shows nothing or only fragments, do not pay hoping saving will repair them: it will not.

How to avoid this next time

Wrong-drive formats usually happen for a boring reason: a letter changed, a reader was swapped, or two drives looked alike in a dropdown. Before any format, match the drive by size and label in Disk Management, disconnect drives you do not intend to format if you can, and read the confirmation prompt slowly. Guiformat formats an existing partition, and it does not ask twice in a way that protects you from a wrong letter. The check has to happen before you click Start.

Backups are the other half of prevention. A single copy on a card is not a backup. A second copy on a different drive turns a wrong-drive format from a disaster into an inconvenience. Make that second copy before the next format, not after.

What NOT to do

• Do not write anything to the formatted drive, including recovery software, recovered files, or test files. Every write can overwrite recoverable data.
• Do not format the drive again, to FAT32 or anything else, hoping to undo the first format. A second format makes recovery harder, not easier.
• Do not run disk repair or partition repair tools on the formatted drive before a recovery scan, unless you understand what they change. Repairs can rewrite structures that recovery software needs.
• Do not keep the drive in daily use while you decide. Continued use writes logs, thumbnails, and other data onto it, even when you are not copying files deliberately.
• Do not promise yourself, or anyone else, that recovery will work. It may work, it may work partly, and after a full format or new writes it may not work at all.

If this did not work

If a scan finds nothing useful, assess the value of the data. For replaceable downloads, accept the loss and restore from a backup if you have one. For irreplaceable photos or work, stop using the drive and consider a professional service before trying more tools: it is not cheap and not guaranteed, but least likely to make things worse.

If recovery software finds some files but not others, save what is good to a different drive immediately. A partial recovery is still a recovery; do not lose it to a later write.

This site is unofficial and unaffiliated with RidgeCrop and Microsoft. Guiformat is Windows-only, formats an existing partition to FAT32, and does not install anything. The recovery links above go to vendor sites; we do not claim a commission from them, and no recovery tool can promise a result after a format.

FAQ

Can I undo a format? There is no undo button. Recovery software may find file data left behind by a quick format, but it cannot reverse the format itself, and it cannot recover data that has been overwritten.

Should I try several recovery tools? Trying a second scan from an image is reasonable. Installing several tools onto the formatted drive, or saving to it, is not: those writes can destroy what a later scan might have found.

Is free recovery really free? Many tools offer a free scan and preview, with paid recovery for saving files. Read the pricing before you scan, so a preview you rely on does not turn into a surprise charge at the saving step.

When should I use a professional service? When the data is irreplaceable, when scans find nothing, or when the drive itself is failing. In those cases, further home attempts can reduce what a professional can recover.

Related fixes

• Failed to open device, GetLastError() = 32
• Drive missing from the guiformat dropdown
• How to format an SD card to FAT32
• Get FAT32 GUI Formatter