try any of these:
http://www.3dchipset.com/utilities/nvidia/driver_removal/index.php
also- go to Control panel - system - hardware - device manager -display adapters: right click on card, Uninstall.
shut down pc, unplug, pull out old card, put in new- reboot (unless there's instructions in the radeon manual saying that you need to install the drivers before you install card)
http://www.3dchipset.com/utilities/nvidia/driver_removal/index.php
also- go to Control panel - system - hardware - device manager -display adapters: right click on card, Uninstall.
shut down pc, unplug, pull out old card, put in new- reboot (unless there's instructions in the radeon manual saying that you need to install the drivers before you install card)