So, I just changed graphics Card from a GeForce 560 ti to a GeForce Gtx 660 ti. I also removed the CPU cooler to dust it off, because it was extremely full of it. When I started the computer everything ran smoothly until I started World of Warcraft about two hours after start up. After about 10-15 minuters of playing the computer just shuts down (like if someone had pulled out the power cord). I got extremely shocked, so I booted up My PC. I Waited a while before trying to play WoW again, but when I got around to it the same thing happened; it shut down after 10-15 minutes of playing.
What can this be? My first thought was that My PSU was too weak. I have a Corsair cx 600W which should be enough? Could I have ruiner the cooling paste on the CPU cooler when I removed it?
Ess is right if you removed the cooler from the CPU and just put it back on that could be your problem. Though I would expect your system to throttle down 1st before shutting off. What is the watt and AMPs requirements for both VGA cards. In the short term you could try putting the old VGA card back and see if your system still shuts down.