I would bet overheating of the video processor or the system CPU itself (or both)
Hamluis is right - if either of those overheat, you may not get any kind of message, no BSOD, etc. Let it sit for a while and you will be running again - for a while. My BIOS has a setting that if my CPU gets about X degrees, it just shuts down (hopefully). Hopefully it will shut itself off before it cooks itself.
You can download some free software to monitor temperatures of such things, see what the max temp is for your video and CPU and keep an eye on it while you are gaming. It will most likely go up and you can watch it.
I have no recommendations or personal favorites. Speedfan is one, but there are others that are probably more exciting:http://www.almico.com/speedfan.php
I have seen where especially
gaming will run up these temps and you can sometimes just upgrade your cooling fans to get more airflow or even go liquid cooled (Prestone
?). Systems can be designed and modified with gaming in mind. Maybe your system was designed with general purpose in mind if it works okay until the games begin.
Games can be intense and demanding of resources these days.
Edited by joseibarra, 19 November 2009 - 05:14 PM.