Uninstall the previous driver...reboot....install new driver...reboot...go back to what I was doing
+1
That's exactly how I do it as well.
I also installled the 177.92 drivers and have had great success with them. Turning on physics acceleration was a lot of fun in UT3. Also Nvidia has a UT3 physX mod for anyone with UT3, offer 3 different maps that have object that break more realistic. UT3 Mod