Make sure that the hard drive in question is not mounted INSIDE another hard drive. You can check this on Windows XP by going to My Computer. If you do not see your hard drive listed under "Hard Disk Drives," but you do see it inside another drive, you need to assign a new letter and path. Right-click on My Computer and go to "Manage." Select "Disk Management," right-click on the volume of the hard drive in question, and choose "Change Drive Letter and Paths..." Remove the current configuration, then choose "Add..." and add a fresh letter.