I've been trying to fix a desktop pc which doesn't heat up the processor (not getting connection to) during boot up/pressing power on button. This has occurred before and removing all components and adding them again has fixed it twice but I need to know what might be causing this or which part/s may be faulty and prevent it from hapening again. The processor is a Intel p4 2.8 Ghz. Motherboard: Intel Desktop Board D865GSA
When the system isn't working, when pressing the power button, the fans rotate but the system turns itself off after a couple of seconds. I tried removing the heatsink and touching the processor but there doesn't seem to be any heat generation. I've tried other PSU once but it didn't help.
I suspect something on the mobo has malfunctioned or something. Any help would be appreciated?
EDIT: i'm not implying why the processor isn't heating up if the mobo is running. I'm asking what might be stopping the connection to the processor to stop it from running in the first place.