Go to System Properties, Advanced Tab, Startup & Recovery Settings and uncheck "Automatically Restart". Next time your system encounters the error you'll see a blue screen instead of rebooting. Tell us what the error on the blue screen is.
You can also look in the event viewer and see what errors you are getting.
i updated everything and it was still rebooting.
eventually, i found it was my intellipoint software.
i was using version 4.0 i think (possibly 4.1)
anyway, try deactivating intellipoint software if u have it.
other than that, try to run it with nothing else running, but i'd bet my ass thats the problem....
Check your power supply ( as suggested above). I had the same problem playing wolf after I installed some new ram. Wasn't enough juice to keep everything happy. I upgraded to a 400w PS and everything is smooth.
My harddrives were cooking a few times and caused alot of errors. I went out and picked up two HD coolers, its just a small heat sink with two fan that blow on the hardrive. Check out coolerguys.com.
If you have the case open and after you shut down, just kinda feel the harddrive and see if its really hot. There are a few software temperature monitors, but I really don't trust them.
There are alot of limitations on cooling based solely on the case. SOme R&D case designers really don't think about airflow too well. I now have a front fan blowing in, hitting the harddrives, and an exhaust (12cm fan just turned around) blowing out the back.
I used to keep the sides of my computer off, but its just a dust magnet then. There has been many of times I just cracked the sides open and put a desk fan blowing right in there. Its not the best things to do, last resort maybe? but it works.
Fans are cheap, but depending one the mother board, you have a limited number of the 3 pin fan connectors. 4 pin are available if you have a few extra power sockets free.