I took out the CMOS battery and it reset and whatnot. I took out every card and put them in one by one as I booted the computer, and it booted fine every time. I think I've further narrowed down the problem though. Two days ago I spilled iced tea all over my wonderful keyboard. Well some keys stopped working, so I was using my mom's keyboard off of her ancient PII 266. Apparently the computer just refuses to boot with my mom's keyboard plugged in. It boots with no keyboard plugged in, or with my now-destroyed keyboard plugged in. However if I boot with my tead-up keyboard plugged in, the BIOS gives me a 201: STUCK KEY error or something and beeps like crazy, but then lets me boot, and then all the keys work except the numberpad and both shift keys (why the shift keys don't work is beyond me, I only spilled a little bit of tea on the numberpad, nowhere near the shift keys; one shift key does nothing now when pressed, and if I press the other one and type, no keypresses at all are registered by the computer). But whatever. The way to get the computer to boot and be usable is to plug in my old destroyed keyboard, turn on the computer, wait until the bios loads and finds the keyboard and gives me STUCK KEY errors, then yank out that keyboard and plug in my mom's keyboard between the time it starts booting and the time my boot loader kicks in.

My only question now is, is there any sane reason a computer should hang during the BIOS load just because a certain kind of (as far as I know standard) keyboard is plugged in? Or is it just a huge coincidence that doing my keyboard-swapping happens to boot the computer fine. I expect my motherboard to implode any day now.