[SpiritWarrior]

Hmmm.

Try the heatsink fan as your final eliminator firstly. Then, if it doesn't work, it is the processor. Remove the heatsink and check the processor thermal paste. Sometimes thermal paste can get so hot it can actually melt and crack which would result in you burning your chip. Check these things foremost. You basically ran down the list of options. My first instinct said HD and possibly mobo but you said you replaced both, so i'm left with processor only. The reboot before post - if it is an overheating issue it is a severe one (i.e. thermal paste not present).

If you find that the paste is not there or is burned off, then it is possible re-applying some will fix it, or you could have simply fried your chip. I have had that happen before.