I should mention that it's not only documents that are showing Windows 7's instead of XP's... it seems to be anything in the x:\documents and settings folder, including my XP user account's desktop.
Ex: I should see my XP desktop icons in the x:\documents and settings\user\desktop folder, however instead my Vista desktop icons are displayed instead. And yes, I'm totally certain that XP's files are in that location; my x: drive is where WinXP, user documents, and all programs installed under XP are located. All of Windows 7's files, documents, and programs are installed on c:. If I do a computer-wide (not just a drive-wide) search, none of those XP desktop icons or documents appear... nothing from x:\documents and settings as far as I can tell.