Did the event viewer, found an error around 8:30AM telling me there was a bad block on my hard disk. Then around 9:50 a whole bunch of logs telling me that programs had restarted, including a suspicious one saying the computer has rebooted from a bugcheck. Went to defrag, since I can't recall when I last did that - and I couldn't defrag, didn't have the available space on the hard drive to run it. Got rid of a bunch of stuff and defragging now. I'll let you know if I still get any shutdowns/reboots in a day or two or if the defragging and file deletions solve the problem. (oh, and PC temp is holding steady at 93, even after running a torrent for a couple hours, so I'm ready to rule out temperature)