Ok I was using my computer and it randomly shut off. I went to boot and it instantly shut it self off. Tried that again with same result. I came back to five minutes later started it up and again same thing but it went further into boot.

So My suspicion is something has overheated I got into the bios very quickly and the CPU temp reads 169F. I think that is obviously the problem. However I left the computer off all night and then came back to it went immediately into bios and the temperature was the same. the computer thne shut itself off about 10 seconds later. I'm wondering how it got to 169 to room temperature immediately. Is there something else wrong here?

Here is the hardware: ASUS p5w DELUXE
CPU: INTEL Q6700 2.6 ghz quad core
Power Supply: Antec 500 watts
4GB of RAM
2x SATA 750GB HD
1x IDE optical drive

My belief initially was ok the the CPU heatsink was somehow moved and is no longer working effectively (I've been using this machine for about 7 months no problem). But I think its strange that the temperature rose that much even after it was off all night. Is the CPU damaged? Is the temperature sensor damaged? Should I just replace the heatsink or the cpu as well? Or am I totally wrong assuming its the CPU temperature?

Thanks any help will be appreciated!