GeForce 9400gt 1gb vs Dell E310

I have a Dell E310, 2g ram, 400W PSU, and can not get the GeForce 9400GT 1 gb PCI card to work. System freezes (will not boot) when the card is installed. The only way to get the system to boot is to unistall PCI Bus through device manager, power off, install 9400gt and then the system will boot. Bad news is because I unistalled PCI bus, I now have no keyboard or mouse because the USB ports don't work. (E310 has USB for mouse & KB). Help!!! Any suggestions? The only error I've noticed is a "04/00/00 Pmem" I don't want to buy another computer just to get the card to work.
CowboyG

Yes, that was the first thing I did. I even went with a Dell PSU (which cost me more) to make sure PSU wouldn't be an issue. I also pulled the audio card that I had installed off so that the only thing I had attached was the 9400gt.