I'm guessing you got an intermittent failure, they're a b!tch to find, cause they'll pass most checks. Get mem-test and see if its your memory, if it passes then under clock your video card and see if it goes away. Then cpu stress test. Alot of times things won't just burn out, but slowly act up more and more until they finally give out.
Your cpu has a temp sensor built in, it should be listed in the bios. A program like motherboard monitor should allow you to view it in windows. Use that one instead