My computer froze last night, so I shut it off, and now it won't turn back on again.

I can hit the switch, and the computer lights up for a minute, but before the POST even starts, it shuts itself off again.

I don't suppose anybody can tell me where the problem lies? I tried disconnecting everything except the processor, and it still won't stay turned on...although it beeps at me if the video card and/or RAM is disconnected.

EDIT: Please ask all relevant questions at once--I'll only be able to come online and check this thread once per day.