Like I said before get some thermal grease cleaner. Clean the old paste off, remove the pad, then put a bb sized dab of thermal grease in the middle of the cpu or processor (one not both!). Then attach the heatsinkand tighten it down. When your tightening the thermal grease will be spread out. Turn on your pc and see if everything goes ok.
i think i know why it keeps turning off, because i checked on asus's website and my cpu wasn't on the supported cpu list. so i'm returning the MOBO. Some i need another MOBO any ideas? (needs to have pci-e, ddr1 not ddr2, supports 775 and ht and between £30-40/$55-65)