Try replacing all heatsink compounds and the old cover off, point a fan at the open box test. After that you are looking at new boards, etc.
Frnds my pc keeps turning off after 4-5 min on gaming and giving blue screen.. I have dell xps tower qx6800 2.9 with 8 gig of ram.. 2 gb gtx 650 ti.. My supply is 1000 watts giving 10 amps on 12v to graphic card.. I cleaned my pc everything is good but it keeps restarting or hanging.. Windows 7 all latest drivers..