No guarantees, but it sounds like a driver problem, perhaps a corrupted driver file.
You might want to try using a fresh version of the latest driver for your video card:
http://www.nvidia.com/object/winxp_180.48_whql.htmlBe sure to uninstall the old driver first and then install the new one. Installing a new nvidia driver without uninstalling the old one first can absolutely cause problems down the line.
