Guiformat Failed to Open Device: Fix GetLastError() = 32, Drive Is in Use
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.
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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.