INACCESSIBLE_BOOT_DEVICE — the blue screen, explained and fixed

This stop code (0x0000007B) appears during startup: Windows began booting, then lost the ability to read its own system drive. The drive is usually still fine — the path to it broke. Classic triggers: the BIOS storage mode was changed (AHCI ↔ RAID), a storage driver was replaced by an update, or the boot configuration was damaged.

The fix, in order

  1. Undo any BIOS/UEFI change first. If someone switched the SATA mode (for example from RAID to AHCI or the reverse) while “tuning” settings, switch it back — Windows was installed expecting the other mode.
  2. Boot the recovery environment (it appears after two failed starts, or boot from a Windows USB) → Troubleshoot → Advanced options → Uninstall Updates → remove the latest quality update. An update that swaps the storage driver is the most common recent cause.
  3. Try System Restore from the same menu, choosing a point before the problem.
  4. Use Startup Repair, also in Advanced options — it fixes damaged boot configuration data.
  5. If you can reach a command prompt in recovery, run chkdsk C: /f (the letter may differ in recovery) to rule out file-system damage, and check the drive is detected at all in the BIOS.

If it still happens

If the drive doesn’t appear in the BIOS at all, this stops being a Windows problem: reseat the drive/cables on a desktop, and on any machine, treat it as possible drive failure — recovery of your files comes before repair attempts.

Common questions

Did my hard drive die? Usually not — the drive typically reappears once the storage mode or driver is put back. A drive missing from the BIOS entirely is the worrying case.

It started right after a Windows update. Why? Updates sometimes replace the storage controller driver, and the new one can’t read the disk the way the old one did at boot. Uninstalling the update in recovery is the targeted fix.

Related errors

UNEXPECTED_STORE_EXCEPTION · CRITICAL_PROCESS_DIED · Windows Update error 0x80070002