Have you tried installing the drivers manually? I never use the setup.exe when installing nVidia video card drivers, just to avoid unusual problems exactly like this.
The simplest way is to right-click on the downloaded file, and choose to extract the driver files into a new folder. Then go to the Device Manager, find your Display Adapter category, double-click on the GF3 card, and choose the Driver tab. Then, instead of allowing Windows to try and detect the device and install the drivers, choose a manual installation, and browse to the folder that contains the extracted files. After the driver is located, make sure your video card is identified correctly, and allow Windows to install the necessary files from this location. If the driver update is successful, Windows will prompt you with a request to reboot the system.
You'll need an unzipping utility like WinZip or WinRAR to extract the driver files.
If this doesn't work, you may be forced to download some kind of "cleaning" program (such as <A HREF="http://www.vtoy.fi/jv16/index.php" target="_new">Regcleanr</A>) that will allow you to remove all traces of the antivirus program from the Registry, and/or anything loading in Startup during the boot that might be interfering with the driver installation. It could also be necessary to reinstall the antivirus program, uninstall it <i>again</i>, and reboot before attempting the driver installation, just in case the previous program uninstallation was not a complete success. The application might have had some kind of file corruption that you were not aware of, and the uninstallation might not have functioned correctly as a result.
You failed to mention your operating system version, but if this happens to be Win9x, you might get better results by first uninstalling the video card from the Device Manager, rebooting, and then using the Add/Remove Hardware applet in the Control Panel to first install a standard VGA adapter. After a second reboot, you can then follow the instructions as mentioned above to upgrade the VGA adapter listed in the Device Manager to the SVGA GF3 card by browsing to the folder that contains the extracted driver files. However, this step isn't necessary with Win2K or WinXP.
I'd also suggest, if you are running a version of Win9x, that you reinstall DirectX before attempting the video card driver upgrade, in case there happens to be file corruption with this application as well.
Be advised that if you choose to use something like RegCleanr, it is best to remove Registry Keys manually with this program, instead of relying on an automatic cleanup/fix. If you are using WinXP, this Registry cleaner does an excellent job, and should automatically delete orphaned keys without manual intervention: <A HREF="http://www.lexunfreeware.com/RegScrubXP/RegScrubXP.htm" target="_new">RegScrubXP</A>.