right when the system died, i was playing BC2 and listening to music using the winamp player, the screen froze for maybe 3 seconds mid game play and all audio stopped, then it went to BSOD and at the bottom of the bsod it said PHYSICAL MEMORY DUMP..........
that screen seemed to be stuck so I hard booted the system
when i tried to turn the system back on the mobo wouldnt post, the monitor would go into sleep mode because it couldnt find a video signal/source.
is it likely the problem is the cpu or the mobo in your opinion from what i described
Its a motherboard problem based on your description I say the motherboard has had it.
In the meantime you need to make up your mind if you want to test your old cpu and make sure it works or not.
If I were you I would just leave the lga775 socket hardware alone and move up.