Nvidia just posted a public beta of a driver that sparked quite some controversy in recent days. Version 177.39 is currently the only version to support GeForce PhysX. Nvidia also mentioned that it will be releasing a 177.41 WHQL driver today, which, however, will not include PhySX supported, as it was built before version .39.

The driver download links are:

Windows Vista 32-bit
http://www.nvidia.com/object/winvista_x64_177.39_beta.html ">Windows Vista 64-bit
Windows XP 32-bit
Windows XP 64-bit