I have just built a new PC. I powered it up for the first time and it ran fine. I let it run for a few days before I had a chance to install Win XP. It continued to run fine. Then I figured I'd give my new P4 2.4GHz processor a test and ran music videos from the internet. Again it ran fine for about 15 mins until it shut down. I figured the processor overheated, which it did. Now every time i turn it on, the processor overheats after about 15 seconds. All fans are working fine. Any suggestions?