The ‘Unmountable Boot Volume’ error is caused by data corruption – how to fix it in XP, Vista and Windows 7. This error accompanied by a ‘blue screen of death’ is the result of corruption on the hard drive which can usually be fixed – as long as you have a Windows installation disk (or a Vista/7 Recovery Disk – ask a friend to burn one for you).
What Is An Unmountable Boot Volume? The boot volume is the volume (partition) that contains the Windows operating system files – for most people that will be the C: drive. To ‘mount’ it (start Windows), the computer needs to be able to access that C: partition.
The error occurs because the Windows file system is damaged – so the computer cannot access the data on the C: partition and cannot start Windows. The damage is usually caused by the computer not shutting down properly (e.g. PC froze, crashed or had a power cut) or by software corruption or (most seriously) by hardware failure e.g. a failing hard drive.
How To Fix It – The key to fixing the error is to repair the Windows file system. We will give instructions below for fixing XP and Windows 7 (for Vista, follow the W7 instructions).
Warning: if you do not already have a good backup of all your data we would advise backing up your data using Knoppix first or seeking professional help – if the damage was caused by a failing hard drive on its last legs, the repair procedure could finish it off…
- 1. Configure the BIOS to start your computer from CD/DVD – see our article how to boot from a CD or DVD
- 2. Insert your XP installation disc into the CD/DVD drive and restart your computer
- 3. When you see the ‘Welcome to Setup’ screen, press the R key on your keyboard to ‘repair a Windows XP installation using the recovery console’. This will take you into recovery mode with a DOS prompt.
Tip: if your file system is badly damaged you may not see the next 2 steps, just skip to step 6.
- 4. If asked which Windows XP installation you would like to log into, type in the number of your XP installation (e.g. 1) and press Enter – usually your installation will be listed as number ‘1: C:\Windows’
- 5. If prompted, type in your Administrator password – if it is blank (it usually is) just press Enter.
- 6. Now type chkdsk /r and press Enter (there is a single space between chkdsk and /r). This will start a disk check program to check for and fix any errors on your hard drive – the process may take several hours to complete. Don’t worry if the ‘percentage complete’ figure drops at times e.g. gets to 80% and then drops back to 50% – this is normal, just have patience and it should get there in the end.
- 7. After checking is complete, type exit and press the Enter key to restart your computer into Windows.
If the above process fails to restore the system then repeat from the start but, this time, instead of step 6 step above, type in the command fixboot. You will be prompted to select Yes or No to ‘write a new boot sector to the partition.’ Type Y for Yes and press Enter. Then type exit and press the Enter key to restart your computer into Windows.
Warning: Do not interrupt the disk checking process once it starts or you could make the file system corruption even worse – if using a laptop make sure it is plugged into the mains.
Windows 7 (and Vista)
- 1. Configure your BIOS to start the computer from CD/DVD – see our article how to boot from a CD or DVD
- 2. Insert your W7/Vista installation disc into the CD/DVD drive and restart your computer.
- 3. The CD will start loading – at the first ‘Install Windows’ dialog box, when prompted to select your Language, just click ‘Next’
- 4. When you see the second ‘Install Windows’ dialog box, select ‘Repair My Computer’ at the bottom to start repairs – do NOT click the ‘Install now’ button!!!
- 5. If the first ‘System Recovery Options’ dialog box appears, select your operating system when prompted and click Next
- 6. In the second ‘System Recovery Options’ dialog box, select ‘Command Prompt’ to take you into a DOS prompt
- 7. At the command prompt type in chkdsk /R C: where ‘C’ is your Windows partition. (Note: there is a single space between chkdsk and /R and another space after /R)
- 8. You will be asked if you want to check the hard drive the next time the computer starts – type in Y to confirm
Restart the computer – Windows will now check the hard drive and repair the damaged file system – this process may take several hours to complete.
If the above process fails to restore the system then repeat from the start but, this time, instead of step 7 above, type in the command bootrec /fixboot and then restart.
Hopefully this will have fixed the unmountable boot volume error and Windows should now start up normally :-)