FAT_FILE_SYSTEM, the blue screen, explained and fixed

This stop code (0x00000023) means the driver for the FAT file system hit an error it could not recover from. FAT (FAT12, FAT16, FAT32) is what USB flash drives, SD cards, and the small EFI system partition on your boot drive use, so this crash usually involves removable media going bad, a card reader misbehaving, or corruption on that EFI partition. The NTFS partitions holding most of Windows are covered by a different code, 0x24.

The fix, in order

  1. Remove removable media and reboot. Unplug USB sticks, SD cards, and external drives, then start the PC. If it boots cleanly, the problem device is in your hand, and the internal drive is fine.
  2. Copy data off the suspect stick or card before repairing it. Plug it into another port or another computer and copy everything off first. Repair tools write to the disk; a failing card can die mid-repair, and data recovery comes before file-system repair.
  3. Run chkdsk on the volume. Note its drive letter in File Explorer, then from an admin Command Prompt: chkdsk X: /f (replace X). chkdsk can fix the directory and allocation-table damage that triggers this code.
  4. Try a different reader, cable, or port. SD card readers and USB hubs are cheap failure points. A card that errors in one reader and reads perfectly in another has told you the reader was the fault.
  5. If the crash happens with nothing plugged in, the EFI system partition is the suspect. From the recovery menu’s Command Prompt, run chkdsk against the EFI partition after assigning it a letter with diskpart, or use Startup Repair, which checks it automatically.
  6. Retire media that keeps corrupting. A flash drive or SD card that produces this error repeatedly is worn out. Flash memory has a finite write life, and file-system corruption is how the end usually looks.
Do not format as a first step. Formatting is offered by Windows the moment it sees a damaged FAT volume, and it destroys the file table your data recovery depends on. Copy first, chkdsk second, format only a card whose data is safe or worthless.

If it still happens

If a specific card or stick checks out clean on another machine but crashes this one, update the chipset and USB controller drivers and test the reader hardware. If the internal EFI partition is the source and Startup Repair cannot fix it, rebuilding the EFI bootloader files with bcdboot from the recovery Command Prompt is the next step, and the drive itself should be health-checked for deeper trouble.

Common questions

Which drives use FAT and can cause this? USB flash drives and SD or microSD cards almost always, external drives sometimes, and the small EFI system partition on every modern Windows boot drive. Your main Windows partition is NTFS, so a FAT blue screen with nothing plugged in points at that hidden EFI partition.

Will formatting the card fix FAT_FILE_SYSTEM for good? Formatting rebuilds the file system, so it clears the corruption, but it erases the card and does nothing about worn-out flash. If the same card corrupts again after a format, replace it; the card is at the end of its life, not in need of another repair.

Related errors

NTFS_FILE_SYSTEM · KERNEL_DATA_INPAGE_ERROR · INACCESSIBLE_BOOT_DEVICE · CRITICAL_PROCESS_DIED