No video upon boot up.

I currently had a friend come to me, and asked me to put in the new PCI video card he had just bought into his HP Pavillion 501n. He has XP loaded on his machine. So I installed the card, went into control panel, system, device manager, displayand I thought i disabled the current onboard video it had. I rebooted, but the onboard video was still working. So i went back to device manager, display, and made the mistake of disabling VGA. When I booted up, I came up with a blank screen when itloads the OS. I tried Safe Mode, it gets stuck. I tried Enable VGA, and the black screen remains after it starts to OS. I’m lost, and need help. Thanks in advance.