Seemingly random crashes: Please Help!!?

This has been happening for about a week now (I've been trying things and just can't get it to stop). My computer (seemingly at random), restarts itself.

When Windows (XP), comes back up, I get the box "The system has recovered from a serious error." I click Send Error Report. It says something about not knowing what the specific problem is, but that it could be because of a device driver.

When searching on a search engine with my symptoms, the common theme for the problem seems to be device drivers as well. So, that was what I tried to fix. I updated my sound and video card drivers. I downloaded software (Driver Genius), which suggests driver upgrades...and upgraded all the suggestions. I've gone into control panel and turned off audio hardware acceleration. Nothing works.

The restarts can happen when I'm watching video and surfing the web, it always happens at least once while I'm sleeping and the computer is doing essentially nothing. It isn't a temp issue because SpeedFan tells me my comp temperature at all times (and as mentioned, it will restart in the middle of the night when nothing is happening).

I read on another forum about how using minidump files can help figure out the problem, but I don't know what that is. Can anyone help me? Can you suggest what I can try next? Can you direct me to some information I can give that will help you help me? Thanks for any advice.