How to Fix UNMOUNTABLE_BOOT_VOLUME Error in Windows 11 (9 Proven Fixes)

Windows 11 PC won’t start and displays a blue screen UNMOUNTABLE_BOOT_VOLUME error? It usually means Windows can’t access the drive that contains the operating system. Since it can’t locate the boot drive, the startup process stops, and your computer enters a restart loop or remains stuck on the recovery screen. You may experience this error after an unexpected shutdown, a failed Windows update, file system corruption, bad sectors on the SSD or hard drive, damaged boot files, or failing storage hardware. In some cases, it may also occur after changing BIOS settings or replacing storage components. In this guide, you’ll learn what causes the UNMOUNTABLE_BOOT_VOLUME error in Windows 11 and how to fix it so your computer boots normally again.

What Causes the UNMOUNTABLE_BOOT_VOLUME Error?

The UNMOUNTABLE_BOOT_VOLUME error displays when Windows cannot access the partition where the operating system is installed. This prevents Windows from loading the files it needs to start, so the computer stops with a Blue Screen of Death (BSOD).

Common causes include:

• Corrupted file system – If the file system on the Windows partition becomes corrupted due to an improper shutdown, power outage, or software crash, Windows may be unable to read the boot drive.
• Bad sectors or a failing SSD/HDD – Storage drives can develop bad sectors over time. When critical Windows boot files are stored in these damaged areas, the operating system may fail to start.
• Damaged boot files or Boot Configuration Data (BCD) – The Boot Configuration Data tells Windows where the operating system is located. If these files become corrupted or are accidentally modified, Windows may fail to load the boot volume.
• Interrupted Windows update – If your PC loses power or restarts unexpectedly while installing a Windows update, important startup files can become incomplete or corrupted.
• Loose or faulty storage cable (Desktop PCs) – A damaged SATA cable or loose connection can interrupt communication between the motherboard and the SSD or hard drive, preventing Windows from accessing the boot drive.
• Incorrect BIOS or UEFI settings – Changing storage-related settings, such as SATA mode (AHCI/RAID), boot mode, or boot order, can stop Windows from finding the correct system partition.

Before You Start Troubleshooting

Since this error usually prevents Windows from starting, you’ll need to access the Windows Recovery Environment (WinRE) to perform most of the fixes below.

If your PC doesn’t automatically open the recovery screen after several failed boot attempts:

1. Turn on your PC.
2. As soon as the Windows logo appears, hold the Power button until the PC turns off.
3. Repeat this process three times.
4. On the fourth startup, Windows should load Automatic Repair.
5. Select Advanced options to open the recovery tools.

If WinRE doesn’t appear, start your computer using a Windows 11 installation USB and select Repair your computer instead of Install now.

1. Run Startup Repair

If the UNMOUNTABLE_BOOT_VOLUME error appeared after a failed update, unexpected shutdown, or power outage, Startup Repair is the best place to start. It automatically checks for missing or damaged startup files and attempts to fix common boot problems.

• Boot your PC into Windows Recovery Environment (WinRE).
• Select Troubleshoot > Advanced options > Startup Repair.

• Choose your Windows 11 installation if prompted.
• Wait while Windows scans and repairs startup issues.
• Restart your computer.

If Windows starts normally, no further troubleshooting is needed. If you still see the UNMOUNTABLE_BOOT_VOLUME error, apply the next solution.

2. Check the Boot Drive for File System Errors

A corrupted file system or bad sectors on the Windows drive can prevent Windows from accessing the boot volume. Running CHKDSK scans the drive for errors and attempts to repair them.

• Boot into Windows Recovery Environment (WinRE).
• Go to Troubleshoot > Advanced options > Command Prompt.

• Identify the Windows drive letter. In WinRE, it may not always be C:.
• Run the following command (replace C: with the correct drive letter if needed):

chkdsk C: /f /r

• Wait for the scan to complete. This may take some time, especially on large drives.
• Restart your computer.

If CHKDSK repairs disk errors and Windows starts normally, the issue was likely caused by file system corruption. If the error persists, continue to the next solution.

3. Repair Corrupted Windows System Files

If Windows system files become corrupted, your PC may fail to access the boot volume during startup. Running the SFC and DISM tools from the Windows Recovery Environment can repair these files.

1. Boot into Windows Recovery Environment (WinRE).
2. Open Troubleshoot > Advanced options > Command Prompt.
3. Run the following command to check and repair system files:

sfc /scannow /offbootdir=C:\ /offwindir=C:\Windows

Note: If your Windows installation uses a different drive letter in WinRE, replace C: with the correct drive letter.

4. After the scan finishes, restart your PC and check if Windows boots normally.

If the error continues, repair the Windows image by running:

DISM /Image:C:\ /Cleanup-Image /RestoreHealth

Restart your computer once the process is complete. If the UNMOUNTABLE_BOOT_VOLUME error still appears, move on to the next solution.

4. Rebuild the Boot Configuration Data (BCD)

If the boot configuration files are damaged or missing, Windows may be unable to locate the operating system, resulting in the UNMOUNTABLE_BOOT_VOLUME error. Rebuilding the Boot Configuration Data (BCD) can restore the required boot information.

1. Boot into Windows Recovery Environment (WinRE).
2. Open Troubleshoot > Advanced options > Command Prompt.
3. Run the following commands one at a time:

bootrec /fixmbr
bootrec /fixboot
bootrec /scanos
bootrec /rebuildbcd

4. If Windows installation is found, type Y to add it to the boot list.
5. Restart your computer.

If you receive an “Access is denied” error while running bootrec /fixboot, skip this step and continue with the next solution. The issue can usually be resolved using the bootsect command or by rebuilding the EFI boot files.

5. Restore Your PC Using System Restore

If the UNMOUNTABLE_BOOT_VOLUME error started after installing a driver, Windows update, or changing system settings, restoring your PC to an earlier restore point may fix the problem without affecting your personal files.

• Boot into Windows Recovery Environment (WinRE).
• Select Troubleshoot > Advanced options > System Restore.

• Choose your Windows account and enter your password if prompted.
• Select a restore point created before the error first appeared.
• Follow the on-screen instructions to complete the restore process.

Your computer will restart automatically after the restoration is complete.

If the error still occurs or no restore points are available, continue to the next solution.

6. Uninstall the Latest Windows Update

If the UNMOUNTABLE_BOOT_VOLUME error appeared immediately after installing a Windows update, removing that update may restore normal startup. This can happen if the update is interrupted or causes compatibility issues with your system.

• Boot into Windows Recovery Environment (WinRE).
• Select Troubleshoot > Advanced options > Uninstall Updates.
• Choose one of the following options:
  • Uninstall latest quality update (recommended first)
  • Uninstall latest feature update (if the problem started after a major Windows upgrade)

• Follow the on-screen instructions.
• Restart your PC.

If Windows starts normally, pause Windows Update for a few days before installing updates again.

If uninstalling the update doesn’t resolve the problem, continue to the next solution.

7. Check Your SSD or Hard Drive Health

If the UNMOUNTABLE_BOOT_VOLUME error keeps returning after repairing Windows, your SSD or hard drive may be failing. A drive with bad sectors or hardware faults can prevent Windows from reading the files required to start.

If you can access Windows, use a drive health monitoring tool to check the SMART status of your SSD or HDD. Most drive manufacturers also provide free diagnostic tools for testing their storage devices.

If the diagnostic tool reports a failing drive or a large number of bad sectors:

• Back up your important files as soon as possible.
• Replace the SSD or hard drive.
• Reinstall Windows on the new drive or restore your system from a backup.

If the storage drive passes all health checks, continue to the next solution.

8. Reset BIOS or UEFI Settings

If you recently changed BIOS settings, such as the boot order, SATA mode, or storage configuration, Windows may be unable to access the boot drive. Restoring the default BIOS settings can resolve the UNMOUNTABLE_BOOT_VOLUME error.

1. Restart your PC and enter the BIOS/UEFI setup (usually by pressing Del, F2, or F10 during startup).
2. Find the option to Load Setup Defaults, Load Optimized Defaults, or Restore Default Settings.
3. Save the changes and exit the BIOS.
4. Restart your computer.

Note: If Windows was originally installed using AHCI mode, don’t switch the SATA controller to RAID or IDE, as this can prevent Windows from booting.

If resetting the BIOS doesn’t fix the problem, proceed to the final solution.

9. Reset or Reinstall Windows 11

If none of the previous solutions resolve the UNMOUNTABLE_BOOT_VOLUME error, Windows installation may be too damaged to repair. Resetting or reinstalling Windows can restore the required system files and boot configuration.

Reset Windows 11

1. Boot into Windows Recovery Environment (WinRE).
2. Select Troubleshoot > Reset this PC.
3. Choose Keep my files if you want to keep your personal data.
4. Follow the on-screen instructions to complete the reset.

If the reset fails or Windows still won’t boot, perform a clean installation using a Windows 11 installation USB.

Important: Before reinstalling Windows, check your SSD or hard drive health. If the storage drive is failing, reinstalling Windows won’t solve the problem. Replace the drive first to avoid repeated boot errors.

Frequently Asked Questions