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INACCESSIBLE_BOOT_DEVICE

Microsoft Windows

Severity: Critical

Source: OnlyErrorCodes.com — Every error code. One place.

Windows INACCESSIBLE_BOOT_DEVICE BSOD — Stop Code Fix

What it means

Windows BSOD 'INACCESSIBLE_BOOT_DEVICE' is the bug check with stop code 0x0000007B, documented on Microsoft Learn at learn.microsoft.com/windows-hardware/drivers/debugger/bug-check-0x7b--inaccessible-boot-device.
Microsoft's exact description: 'the Microsoft Windows operating system has lost access to the system partition during startup.'
The most common triggers are a recent Windows Update that left the BCD in a bad state, a SATA / NVMe controller mode change in BIOS (AHCI vs RAID vs IDE), or a failed driver update that broke storage access at boot.
The fix is Microsoft's recovery sequence using Startup Repair, then chkdsk and BCD repair from Windows Recovery Environment.

Affected Models

  • Windows 11 (every version)
  • Windows 10 (every version)
  • Windows Server 2016 / 2019 / 2022 / 2025
  • Most common after Windows Updates, BIOS changes, or after moving the system drive to new hardware
  • Bug check 0x7B has the same fix sequence across all supported Windows versions

Common Causes

  • Recent Windows Update interrupted partway through, leaving boot files in inconsistent state
  • BIOS SATA/NVMe controller mode changed (AHCI to RAID, or vice versa) — Windows boots only with the mode it was installed under
  • Boot Configuration Data (BCD) became corrupt
  • Storage controller driver updated to a broken version
  • Failing SSD or HDD where the boot partition lives

How to Fix It

  1. Boot from Windows install media.

    If the system is stuck in the BSOD loop, you need Windows Recovery Environment from external media.
    Use Microsoft's Media Creation Tool on another PC to make a Windows install USB.
    Boot from it on the failing PC (F12 or similar during POST for boot menu).
    Choose 'Repair your computer' > Troubleshoot > Advanced options.

  2. Run Startup Repair.

    From Advanced options, choose 'Startup Repair'.
    Windows runs an automated diagnosis (5-30 minutes).
    It can repair the BCD, fix file-system issues on the boot partition, and re-register the boot files.
    Restart afterward.
    This is the single most effective fix for INACCESSIBLE_BOOT_DEVICE — try it before any of the manual command-prompt steps.

  3. Check BIOS for changed SATA/NVMe mode.

    If you recently entered BIOS for any reason, check the storage controller mode.
    It's usually under Advanced > SATA Configuration or Storage > SATA Mode.
    Common values: AHCI, RAID, IDE.
    Set it back to whatever it was when Windows was installed — typically AHCI for most modern systems.
    Save and exit BIOS.
    If the wrong mode was the cause, Windows boots normally now.

  4. Rebuild the BCD from Command Prompt.

    Boot to Windows install media > Repair your computer > Troubleshoot > Advanced options > Command Prompt.
    Run these commands in order:
    bootrec /scanos
    bootrec /fixmbr
    bootrec /fixboot
    bootrec /rebuildbcd
    Type Y when asked to add the Windows installation.
    Restart.
    This rebuilds the Boot Configuration Data from scratch — clears BCD-corruption cases that Startup Repair couldn't fix.

  5. Run chkdsk on the system drive.

    Still in Command Prompt from Recovery Environment:
    chkdsk C: /f /r
    Replace C: with your Windows drive letter if different (it's often E: or D: from the Recovery Environment side).
    The check takes 30 minutes to several hours depending on drive size.
    Repairs filesystem errors that prevent the boot partition from being read.

  6. Uninstall a recent Windows Update from Recovery.

    If the BSOD started right after Windows Update, from Advanced options choose 'Uninstall Updates' > 'Uninstall latest quality update' (or feature update).
    Confirm and let it finish.
    This rolls back the specific update that broke boot — often the cleanest fix when the cause was a known bad update.

  7. Diagnose drive health if all else fails.

    If Startup Repair, BCD rebuild, and chkdsk all fail to clear INACCESSIBLE_BOOT_DEVICE, the boot drive itself may be failing.
    From a working PC, connect the failing drive externally and run a SMART check (CrystalDiskInfo is a common tool).
    Reallocated sectors, pending sectors, or 'Caution' status all point to a failing drive that needs replacement.
    Back up data while you still can, replace the drive, and reinstall Windows on the new drive.

When to Call a Professional

INACCESSIBLE_BOOT_DEVICE needs Windows Recovery Environment.
If the system was working yesterday and started failing today, this is almost always a software-side fix — Startup Repair + chkdsk + BCD rebuild.
If the system was moved to new hardware, the SATA controller mode mismatch is the likely cause; the BIOS fix takes 30 seconds.
True drive failure is rarer — diagnose with chkdsk and SMART before replacing the drive.

Frequently Asked Questions

I never touched BIOS — why would the SATA mode have changed?

A BIOS update is the most common silent cause.
If your motherboard's firmware was updated automatically by the OEM utility (Asus EZ Update, MSI Center, Lenovo Vantage, Dell Update), the BIOS may have been reset to defaults — including the SATA mode.
The first boot after a BIOS update is the classic INACCESSIBLE_BOOT_DEVICE moment.
Check the BIOS settings against what they were before — many BIOSes default to RAID even when AHCI is correct for your Windows install.
Set it back to the mode Windows was installed under and the boot works again.