Ok So I built this computer nearly 2 years ago and it's generally been very good. Yesterday when i was putting the system under a lot of stress it decided to turn off and when turned back on it said that the cpu had overheated. So I thought I'd tread carefully and only use it for a little while and then put some more thermal paste on the chip and clean any dust out of the heatsink. I did this and re-seated the heatsink and now when I turn on the computer th e monitor says no signal and sometimes now after about 20 seconds the computer turns itself off. The monitor saying no signal is always happening. I have: Q6600 Asus P5B-VM SE ati HD2900XT Enermax 650 noisetaker I Win xp 2gb corsair ram Maxtor 500gb HD Literally all I did was take the heatsink off, clean it, add new paste and put it back on, nothing else in the computer was interfered with. Has the graphics card mysteriously decided to pack up even though it said the cpu was overheating? I'm at a loss - I've made sure everything is in properly and taken steps to stop cpu overheating. Thanks in advance guys.