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Doubtful this is causing your issue but if you took the heatsink off the CPU you will need to (I rarely use the word need) replace the thermal compound. There are stickies on how to.
On to the restart issue, I would try resetting CMOS (after applying new thermal compound). Your motherboard manual explains how or you can follow this guide. http://www.wikihow.com/Reset-Your-BIOS
See if that helps.