Vista - Help! Video Card won't install! Drivers?

I just bought an MSI NVIDIA GeForce N9800GT Video Card, and I'm having problems with the installation...
My computer auto-recognizes the card and installs some driver of its own(??), but it doesn't actually let me use it. So I've tried drivers from three different places (NVIDIA site, MSI site, CD that came in-box) and none of them have worked. Every time it says incompatible display drivers, and something about the driver being incompatible with the VGA driver, or some such thing.
I'm really stuck, and I've never had video card problems before, so this is really frustrating.. Please help me!

UPDATE!!
The error message I'm getting is:
Incompatible display adapter has been disabled.
At least one display adapter on the system has been disabled because its driver is not compatible with the driver for the VGA adapter.

Please tell me that helps?

Did you UNINSTALL the drivers of your Previous card before you plugged this one IN? What kind of card did you have before?

Your explanation is a little vague, why don't you give us a little more info on this? it will help others help you better.

This is the first card I've put in, at first I was using onboard ATI X1250.
And no, I didn't uninstall the onboard drivers, should I?

disable the onboard card before you plug in the new card, the ati drivers will be trying to use hybrid crossfire with the Nvidia card. Which is obviously messing things up for you, uninstall the ati drivers, restart your computer and enter the bios, go into integrated peripherals menu and look for onboard gpu or graphics and disable it from there, save and exit. restart and install your NV card

Thank you, thank you, thank you 100 million times.

glad to be of service