I have an Intel D845WN motherboard with 512MB of PC133 SDRAM. I originally had a 1.6GHz processor and just upgraded to a 2.6GHz processor which is the maxium that it can handle. The PC boots up fine and the processor is recognized in the BIOS and in Device Manager. It seems that once I start opening programs or do anything that taxes the processor at all...it just reboots. The new processor is the only thing that I have changed. Could it be a heat issue? I did not use any thermal grease when I installed the new processor. Any help would be appreciated.