motherboard trouble

I have a sick system.
I had the Windows Vista black screen of death (cursor, but black screen even in safe mode)
There are some hints on internet about graphics driver being messed up.
My plan was to:
1) remove by 7950gx2 video card
2) install another card. I purchased a ati 2400hd, which I hope to return after fixing the problem
3) remove nvidia graphics driver
4) make sure everything is ok
5) add 7950gx2 back in

My mobo is intel D975XBX.
The problem is system will not post without the 7950gx2 in. With no video card or with the 2400hd in, it doesn't get anywhere. I put my 7950gx2 back in (even without power), it can get to bios.

I have tried to clear cmos, by removing power and battery, and setting jumpers, but no changes.

Any thoughts?