Hello All. This is my fist post - so forgive me if I'm posting in the wrong place. Motherboard ECS P4M800-M7 (v3.1) (LGA 775 /DDR) Bios : Latest from ECS website CPU: Pentium D 935 OS: Windows XP Home Bios settings : All Defaults I built the system with above motherboard and Pentum 4 2.8 GHz CPU with 1.5G RAM. The system was running fine for past 2.5 years. I decided to upgrade the system and bought used Pentium D 935 3.2 GHz . I'm using the stock fan and heat sink that I received with Pentium 4 2.8 GHz for the new processor and Arctic Silver 5 thermal compound. System starts booting up , shows new CPU in BIOS, OS starts loading and if I'm lucky, it actually completes loading and I can log in. The system stays up for maximum of 2 minutes and then powers off or restarts. Sometimes it happens even before OS completes loading. I'm not running any CPU intensive applications. I'm not even running any applications. Max CPU usage recorded is 8%. Speedfan shows temperature in the range of 38-42 C . Bios shows around 47. What may be going wrong ? Any ideas? Thanks !