I spent the rest of the night wiping and completely reinstalling everything on my gaming box. Well, not everything; tonight I could only get the OSes (XP SP3 on one drive, 64-bit Vista on the other), the usual updates, drivers, and Spore installed.
Spore was one of the reasons I did this wipe in the first place, since it and Mass Effect hated something about the previous install, and now…it works. No time left to actually play with it tonight, though.