Duron/MSI setup stopped working

[ghostman]

I have a whole bunch of computer problems right now. After backing up 6GB of data from one HD to another, my computer screen went blue (not the typical BSOD, just a blank, blue screen). I had to hit the reset button because nothing else worked. Now, the system won't POST. The system is a 750Mhz Duron/MSI MS-6340. I yanked a working 1Gz Athlon/Biostar M7KVD from the lab and swapped CPUs. Both machines now work. I return everything to it's place, and the Duron/MSI setup still won't work.