Windows 2000 on my Dell Optiplex GX400 has a frequent but intermittent issue of failing to boot due to corrupted Operating System files. I am usually able to repair this simply by running chkdsk /r a couple of times on the only drive in the system which has been assigned the drive lettter C:. I am able to reproduce the issue with regularity if I attempt to run Disk Defragmenter on an unmounted volume which apears only in Disk Defragmenter. I am thinking that there is some connection between the existence of this Unmounted Volume and my frequent OS file corruption. For this reason, I would like to eliminate the Unmounted Volume or reassign a drive letter to it in hopes that my frequent file corruption issues will disappear. It is interesting to note that the Unmounted Volume appears only in Disk Defragmenter. It does not appear in Disk Management or My Computer. I only have 1 new, tested good with manufacturer's diagnostics 160GB hard drive in the system which has been assigned the drive letter C: with a single partition which comprises the entire drive. Odder still is the fact that all of the specifications of the Unmounted Volume, in terms of file system, capacity and space are identical to that of the C: drive. Ultimately, my question, then, is: How can I eliminate this issue of frequent OS file corruption? Can I safely eliminate the Unmounted Volume? Should I assign the Unmounted Volume a drive letter? Will either of these actions resolve my original issue or am I on the wrong track?