Fixing mountable/unmountable boot volume in Windows 10

Fixing mountable/unmountable boot volume in Windows 10.

The “Unmountable Boot Volume” stop code in Windows 10 appears whenever your computer is unable to read the HDD or SSD partition that Windows 10 is in. This is another of the many BSOD (Blue Screen of Death) errors that you end up running into. while using a PC.

But, in particular, it can be difficult to deal with the “Unmountable Boot Volume” stop code, since the problem is often caused by data corruption. In almost all cases, a reboot or hard reboot will not work around the error.

If you are stuck in the “Unmounted Boot Volume” boot loop, you should use the Windows Recovery Environment (WinRE) to inspect and repair instances of corrupted data on your computer.

However, to access WinRE, you must have a bootable Windows 10 installation disc or USB drive on hand.

Create Windows 10 Installation Media

If you already have a bootable Windows 10 USB stick or disc, skip. If not, you must create it using the Microsoft Media Creation Tool. For obvious reasons, you need a different work computer to create it. You must also have a USB drive with at least 8GB or a blank dual-layer DVD.

1. Download Microsoft Media Creation Tool.

2. Launch Microsoft Media Creation Tool and accept the license terms.

3. Select “Create installation media (USB stick, DVD or ISO file) for another PC” and click “Next”.

4. Select your Windows 10 language, edition, and architecture. These should match those on the PC with the “Unmountable Boot Volume” BSOD error.

5. Select a USB flash drive. Or choose an ISO file if you want to create a bootable DVD. Insert a flash drive or dual-layer DVD and click Next.

The Microsoft Media Creation Tool will then download the required files. Follow the rest of the onscreen prompts to create a bootable Windows 10 USB stick or DVD.

Boot Into Windows Recovery Environment

Connect or insert a bootable Windows 10 flash drive or DVD into the computer that displays the “Unmounted boot volume” stop code. Then restart your computer and press any key – when prompted at startup – to boot from the installation media.

Note. If your computer does not prompt you to boot from the USB or DVD drive, change the boot order and try again.

After booting from the Windows 10 installation media, click Next on the Windows Setup screen. Then select “Repair your computer”.

On the next screen, select Troubleshoot. You will see the Windows Recovery Environment.

You should return to this screen repeatedly while working on the fixes that follow.

Fix the Master Boot Record (MBR)

MBR, or Master Boot Record, contains information about the operating system and the various partitions on a hard or solid-state drive. It also allows your computer to identify and load the operating system at startup.

Since a corrupted MBR can cause the “Not Mounted Boot Volume” error in Windows 10, you should try to fix it.

1. Select Command Prompt in WinRE.

2. Enter the following commands in the command line console and execute them one by one:

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

3. Close the command line console. Then select Continue to boot Windows 10.

If a corrupted MBR caused the “Unmountable Boot Volume” stop error, you will no longer encounter it.

Perform Start-Up Repair

Windows Recovery Environment provides the ability to automatically repair your computer. If the MBR fix doesn’t work, we recommend that you use it now. Select the Startup Repair option and select Windows 10.

Your computer will try to diagnose and fix problems that it detects automatically. If successful, you should be able to boot to Windows 10 without any problems. If not, return to the WinRE screen.

Run System File Checker

The System File Checker (SFC) tool is a utility that you can run from the Command Prompt console to scan and repair corrupted system files. You must use it on both the boot disk (which is a hidden partition containing boot information) and the partition that contains Windows 10.

Trick; you must first determine the drive letters for the Windows 10 boot drive and drive in WinRE. You will need the DiskPart command-line tool for this.

1. Select Command Prompt in WinRE.

2. Download the DiskPart utility using the following command:

diskpart

After loading DiskPart, run the following command:

list size

3. Determine the letters of the boot drive and drive Windows 10.

Note.

The boot disk weighs about 500 MB, is labeled System Reserved, and usually appears with drive letter C.
The partition containing Windows 10 is the same as the local one drive C that appears in explorer. In WinRE, it may appear with a different drive letter (eg D). You can determine it by the size of the storage.

Make a note of both drive letters. You can find them under the Ltr column.

4. Close DiskPart with the following command:

exit

5. Enter the SFC command, modify it if necessary and press Enter:

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

Note. Replace C with your boot drive letter and D with your Windows 10 drive letter.

The SFC scan may take several minutes. Exit the Command Prompt Console and select “Continue” to then attempt to boot Windows 10.

Run Check Disk Utility

Check Disk Utility (Chkdsk) fixes disk related errors and repairs corrupted data on your computer. You should run it on both the boot drive and the partition containing Windows 10. If you used the DiskPart utility above, you should have already calculated the drive letters for both drives.

However, launching Chkdsk on a Windows 10 partition can take up to an hour or more.

1. Select Command Prompt in WinRE.

2. Run the following command to scan and repair your boot drive:

chkdsk c: / r

Note. Replace c with the letter of the boot drive.

3. Run the following command to scan and repair your Windows 10 drive:

chkdsk d: / r

Note. Replace d with the drive letter of the partition that contains Windows 10.

If the command prompt prompts you to unmount the volume, press Y and then press Enter.

After running the Check Disk utility, exit the Command Prompt console and select Continue to boot Windows 10.

Try Other Recovery Options

If, after installing an incremental update or a feature update, the error “Boot volume not mounted” appears, you can try rolling it back.

Select Remove updates from Windows Recovery Environment. Then select the Uninstall last quality update option to roll back the last incremental update.

If that fails, select the “Uninstall the latest feature update” option to uninstall the last major Windows 10 feature update.

You can also try using the System Restore and System Image Restore options in WinRE to restore your computer to an earlier state. However, to use them, you must have a previous restore point or a system image backup.

Reinstall Windows 10

If none of the above fixes work, you will need to reinstall Windows 10. This will delete all data in the partition containing the operating system. If you have a backup of your data, you can later get your lost files and documents back.

If reinstalling Windows 10 does not resolve the “Unmountable Boot Volume” BSOD error in Windows 10, you may be experiencing a faulty hard drive or another hardware issue. Try seeking help from a certified computer technician.

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