Q8400 Installation problems

Just swapped out a Q6600 for a Q8400 due to a flawed core on my q6600. Anyways, problems began right away and in this order:
1. Boots, says BIOS requires update on my Asus PK5-E, Update BIOS to most recent from flash drive, Installs and verifies installation correctly
2. Boots to windows, try to run Everest Stability Test to help burn in the processor and heatsink, BSOD almost instantly upon start
3. Boots to windows, try to run Windows Experience Index, BSOD instantly
4. Boots past BIOS to windows message that ntoskrnl.exe is corrupted and to put installation disk in to repair file
5. put in installation disk, gives same error, won't proceed to repair option
6. restarted machine, now just blank screen, no BIOS post or anything

Any clues? we realized that only a 4 pin connection was in use on the 8 pin CPU power, so we swapped that for the full 8 pins, thinking it was maybe a stability problem with the CPU, but still not even a BIOS post.

Any help would be great, i have another identical rig, still using the old q6600 oc'd to a comfortable 3.2GHZ running just fine with the same BIOS ver as my crashed rig. This can be used to test out components, but i don't want to shotgun testing, i want to have atleast an educated guess as to what needs to be tested

thanks,
Ryan