SOLVED!

As far as I can tell, all of my hypotheses were dead wrong (which probably explains why no one else knew the answer either). Norton Utilities (Windows) comes with an application called GoBack, by Roxio. The program is intended to facilitate undoing stupid mistakes that cause your computer to have problems (not that I would ever need such a thing, of course ). WinXP has this ability already, but I figured that it didn't cost any more, and might help.

Anyway, as I was clearing off my G: drive in preparation for repartitioning it to accept an HD install, I ran into problems because GoBack installed several MB of hidden files. So, when I deactivated GoBack, I went into Knoppix to use qtparted, and son-of-a-gun, there was my C: drive!! I don't fully understand why GoBack apparently kept Knoppix from seeing an NTFS partition of one drive, but not the NTFS partition of another drive, but it seems that it did. So, in case anyone else has this problem, they can read that it had nothing to do with the make of my computer or the way in which they defined the recovery partition. They can also read that GoBack apparently created many more problems than it prevented