Problem booting windows when video card is in
I've got a 6 year old HP desktop that I'm having problems with. I've stripped it down to just the two HD's (RAID) and DVD drive. It's got onboard everything and works fine like this. The problem is the onboard video is crap. Originally it came with a ASUS GeForce 8500 GT, which worked great for a while. I started having problems which is why I stripped it down to barebones.
So the problem I'm running into is when I install the video card, it recognizes it as the GeForce 8500 GT and searches for drivers. It has no problem at this point displaying anything or booting Windows Vista (32bit.) After it installs drivers, it comes up as "Standard VGA Graphics Card" or something generic like that. I tried installing the original drivers that came with the computer as well as using the newest ones from the nvidia website, and it tells me I have to reboot, of course. I do, and it won't boot Windows. BIOS posts, then the Windows loading screen (with the progress bar) comes up, but when it tries to load the actual GUI it goes to a black screen and reboots itself.
I can boot if I switch the BIOS back to using the onboard video as the primary source, but in the Device Manager it doesn't show my GeForce card anymore, and I have no option to switch when I go to Appearance settings.
Any help with what could possibly be my problem would be much appreciated! Let me know if more info is needed.
-edit- To clarify, when the video card is first installed, it will display through the video card just fine, but in a very low resolution until the drivers are installed.