SmartScreen Windows Protected Your PC When Running Guiformat
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.
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
- 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.
- 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.
- 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.
- 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.
- 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 you see | What it means | What to do |
|---|---|---|
| Windows protected your PC | SmartScreen blocked an unrecognised app | Check source and hash before continuing |
| Publisher: Unknown | File is unsigned | Expect this for guiformat; do not expect a verified name |
| More info, then Run anyway | Allow this one file, this once | Use only after source and hash checks |
| No Run anyway button | File may be known harmful, or blocked by policy | Do not work around it; delete the file |
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.