How to Fix the FAT FILE SYSTEM [fastfat.sys] BSOD Error in Windows?

Hi everyone,
I’ve been encountering a Blue Screen of Death (BSOD) with the message “FAT FILE SYSTEM (fastfat.sys)” on my Windows PC. It usually appears randomly during startup or while using my system, and then my computer restarts automatically.

I’ve tried basic troubleshooting like restarting, checking for updates, and running disk checks, but the issue still persists.

Can anyone explain what causes this error and suggest effective ways to fix it?
Any help or step-by-step solutions would be appreciated!

Tagged: Windows

Windows

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Mira Lennox Lennox

Participant

October 14, 2025 at 9:11 am

Common causes are a failing drive, corrupted files, outdated storage drivers, or even conflicts with third-party software that accesses drives. Start by disconnecting any external drives and see if the BSOD stops. Then, update your storage drivers via Device Manager, run sfc /scannow and chkdsk /f /r on all drives, and check for firmware updates for your drives. If it still happens, test your RAM with Windows Memory Diagnostic and consider running a clean boot to rule out software conflicts. Often, the culprit is either a bad external drive or a driver issue rather than Windows itself.

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