The drive letters are not locked, so when they hooked everything back up your optical drive took over D:\ and your old 20GB D:\ was probably pushed back to, say F:\, which is not displaying in Windows Explorer. You could try random drive letters and see if one responds but that can be tedious and still does not solve the issue of it not displaying. Thus, I'd suggest clicking here to download/install Microsoft's TweakUI. Run the utility, expand My Computer, select Drives, and place a check mark in the box next to any drive that is not displaying a red circle with a question mark in it. That will display all drives currently recognized, including your 20GB partition and all the files it contains.
Hope this helps,
I ( made the mistake of ) taking my system - 1.8GHz P4 - into Best Buy for virus removal after a complete system shut down. It turned out that the problem was a dying disk. I had them install a replacment, but they could not ghost because of the condition of the previous one, so they just installed a basic setup with XP pro.
Problem: The vast majority of my programs and data were on Partitions D:, and E:, both resident on a separate physical drive from the C: which hosted mostly the OS. WHen they installed the new OS, they allowed D: to default to the CD rom. As a result, the machine sees C: and E:, but all of my programs ( & some data ) are on what had been called D:.
How do I ( can I ) recover access to this info? The physical disk is 80G, with former partitions of 20G & 60G. The E: drive still shows 60G, so I have every reason to expect that the info is still present on the invisible partition.