This driver Supports all AGEIA PhysX Processors and GeForce PhysX. This driver will allow you to select and dedicate a GPU to PhysX as well.

• Adds support for NVIDIA PhysX on GeForce 9800 GTX, GeForce GTX 280, and GeForce GTX 260 GPUs, including SLI configurations.
• Experience GPU PhysX acceleration today by downloading the Unreal Tournament 3 PhysX Mod Pack.
• Supports AGEIA PhysX processors and software runtimes (no change to PPU support).
• Supports the following PhysX runtime engines: 2.8.1, 2.8.0, 2.7.4, 2.7.3, 2.7.2, 2.7.1, 2.7.0, 2.6.4, 2.6.3, 2.6.2, 2.6.1, 2.6.0, 2.5.1, 2.5.0, 2.4.4, 2.4.1, 2.4.0, 2.3.3, 2.3.2, 2.3.1
• Includes the latest PhysX runtimes used in the latest game titles

This PhysX driver is bundled in the 177.83 WHQL Drivers which can be found here:

 GeForce ForceWare 177.83 XP (32-bit)
 GeForce ForceWare 177.83 XP (64-bit)
 GeForce ForceWare 177.83 Vista (64-bit)
 GeForce ForceWare 177.83 Vista (32-bit)

We have an article ready explaining GeForce PhysX right here.