Strange Freezing/Crashing

[Vook]

So I was playing TF2 tonight when my computer, all-of-a-sudden, froze for about 8 seconds then rebooted itself. Never done this ever before, and I don't think it was overheat because if it was overheat it would have shut off instantly and stayed off, not 8 sec freeze and reboot.

So during its reboot, while it was showing the "Windows is starting up" (windows 7) with the windows logo....it froze again. 4 seconds on the power button and I reboot it again....it freezes again after I log in. I finally manage to log in and run SpeedFan, and the temps look normal (all 4 cpu cores in the low 40s, gpu at about 55 which is normal), and as soon as I start up MSN, it freezes again. 3 failed reboot freezes later and I finally login and no freeze (so far). MSN started up fine as well.

I still have no idea what caused this, but my only guess is heat issues with cpu/gpu because it was REALLY hot in my room (at least 80 degrees) and I was playing L4D2 for a while as well before TF2. If anyone has any idea what might've caused this, I'd like to know so I can prevent it from happening again.

---------- Post added 2011-07-07 at 08:40 AM ----------

Bump...

Happened again this morning, room was nice and cool and I was only questing by myself, so I doubt it was a heat issue. Took it apart and dusted out the CPU/GPU fans just to make sure, and a couple more freeze-bootups later I'm back on. Only this time, when it froze, I heard the sound stutter really quickly for a couple seconds.

Can someone please help me here? Gonna be kinda hard to raid when my computer is randomly freeze-rebooting and taking 10+ minutes to get back into Windows.