[swdw]

One thing you may be having is driver conflicts as the old drivers were not removed. Switching from onboard to a separate video card can be tricky.

Download the free driver sweeper from guru3d.com or purchase drivercleaner.net

First, I'll describe what you should have done, then I'll explain what you need to do.

When you first swapped, your order of installation should have been.

1. Remove drivers for onboard video
2. Reboot- go to bios and disable onboard video. Turn off palette snoop if on as this will apply to the new card also.
3. Save then shut off computer once it tries to reboot.
4. Install new card
5. boot to safe mode. Decline installing drivers at this point. Check Device manager and make sure only one video card is listed. If 2 are listed still, disable the onboard one. If the onboard chip was ATi or nvidia based, you could have used driver sweeper at that point.
6. Reboot
7. When windows comes up, install drivers

Now, what you need to do is go back almost to square one
1. uninstall the drivers for your new card
2. reboot, go back to the bios and make sure you have memory share functions and palette snoop turned OFF
2. reboot to safe mode, Check Device manager and make sure only one video card is listed.
3. run driver sweeper and remove all nvidia/ati (or other video drivers if you have drivercleaner.net).
4. Reboot
5. install drivers for new video card.

If this doesn't work. Return you system to it's original configuration and start over.

If this doesn't work, take the video card back and try an ATi card. I've seen systems with onboard video where the bridge chipset (talks to the PCi-e or AGP slot) would work with ATi and not Nvidia and vice versa.

Good luck!