Video issue?

[genmasho]

I just upgraded my computer from a nvidia 8800 to a 9800 and added a slot fan underneath it. After installing it I plugged everything back in and turned on the pc, and it I'd running just fine except with the exception that nothing is loading, not even the bios. I have tried to go back to the 8800 and even unplugged the slot fan to if it was a power issues, heather of which worked. Any ideas