Well it's my bro cpu not mine. He got Vista, and he just upgrade his processor to i7, ram to 4g ddr3 and he change his motherboard.
Before he bring it to shop to upgrade his computer, it's fine, but it started freezing when he turn on his computer after the upgrade. His computer will start to freeze after 15-30 mins when he turn on his computer. His graphic card is gtx 8800 I tried checking his cpu heat, but it's fine. My bro even bring it to shop to fix it but ... well they charge him $59 and they only upgrade his graphic card driver which i can help him do it within 10 mins lol. What i think is his norton anti virus is causing the freeze, but i'm not sure.