|Make, Model Number of computer?|
Make & Model number of motherboard?
Age of system?
Did you check the MB capacitors?
Is the CPU & FAN FULLY seated and clipped down onto the MB?
Does it fire without anything attached to it (no RAM, no peripherals - HDDs, DVD/CDs, Floppy etc) to where it might give off beep codes to see if it's working correctly?
Just another stupid saying...