John Barnett Computer Journalist
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How Do I Fix An Unmountable_Volume Error

The Unmountable_Volume error usually occurs because of a corrupt Master Boot record. To remedy this situation you need to repair the MBR. Before you can do this you will need access to the recovery Console via your Windows XP CD.

(Make sure your CD-ROM is set as the first boot option in your BIOS before proceeding. Most new pc's already have the CD-ROM set for first boot option. However, if yours doesn't then you will need to change the boot option in the BIOS. For more details see Question 13 'How Do I Enable CD-ROM Support in the BIOS'

1/ Insert the Windows XP CD into your CD-ROM and Restart your PC. 

2/ The Windows set-up program will begin

3/ When you reach the 'Welcome To Windows' screen press 'R' to start the Recovery Console

4/ For the purpose of these instructions I will assume that you only have one operating system on your hard drive and that that is drive C:/ of harddisk0 (i.e. the first hard drive)

5/ At the recovery Prompt type 1 and press Enter

6/ If you are asked for an administrator's password then type it in at the prompt. If you haven't set a password or you are using Windows XP Home edition then simply press Enter

7/ The Recovery Console will now load

8/ Once the Recovery Console has loaded type 'fixmbr /device/harddrive0' (without the quotes)

9/ Answer Yes to any warning messages by pressing the 'Y' key on your keyboard

10/ After completion Reboot your pc and it should now behave as normal.