just unplug the IDE cable from both drives, and there should be a little jumper somewhere on you motherboard thats labeled CMOS, you move that over 1 pin, then leave it for a minuite and switch it back, that resets your bios settings.
After thats done, boot your computer without the hard drives plugged in
Also you might try the Video card in a different slot. The PCI slot could be bad/damaged. There is also a setting in some CMOS BIOS setups that allows you to power off pci slots when not in use. Can you even get to your BIOS?
Definately try clearing the CMOS first to see if the default settings get you back to normal. Depending on what model of motherboard you have clearing the CMOS is different. Newer Compaqs for instance have a small button you can depress on the MB that allows you to clear the CMOS. Some models (older ones) you just pull the CMOS battery and put it back in.
Others have two pins with a jumper on them, you just remove the jumper like cniv says to do for a minute and replace it. If you picture the CMOS as being a small computer that runs solely on RAM, whenever you interrupt the power to it it completely clears the settings on it. That is the premise behind "clearing the CMOS."