when installing a new graphics card, you need to unsintall the current gfx card driver too then reinstall it. heres how:
1. Unplug nic card or modem from net or disconnect. (I never do this)
2. Disable any AntiVirus Software. If you don't disable, it could give you trouble. (This either)
3. Uninstall current vid driver (If you have an nVidia mobo and a nVidia vidcard, make sure you only uninstall the video driver, not all nVidia drivers or your mobo will lose its drivers also.)
4. Reboot
5. As the reboot comes up, after the quick memory test and hard drives have been recognized, hit F8 and enter "SAFE MODE." On some boards if you hit F8 too early you will enter other utilities.
6. On reboot into safe mode WinXP SP1/SP2 will auto detect and ask you to install drivers. You should be able to can cancel out of the auto install hardware wizard move to step #7. If you can NOT cancel out of auto detect wizard then, navigate to device manager->display adapters->highlight (nVidia, ATI, etc.) and click uninstall or remove but don't reboot. (From Driver Cleaner ReadMe, modified for clarity by Rike)
7. Run Driver Cleaner with the filter for the driver (nVidia, ATI, etc.) you just uninstalled . Quit DriverCleaner and restart into Windows XP normal mode.
8. Install new vid driver. Note for SLI users: sometimes the driver doesn't install for both cards. To ensure proper installation, you should check in Device Manager to be sure the driver is installed for both cards. If it isn't, you should right-click on the yellow-question-marked card and click on Update Driver. (JRd1st)
9.. Empty the recycle bin and Reboot
10. Redo what was undone in #2 & #1, in that order. Reboot if needed to re-establish Internet connection.
11. Enjoy
(source:
http://www.tweaksrus.com/forums/index.php?showtopic=4966)