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.

• Supports for NVIDIA PhysX acceleration on all GeForce 8-series, 9-series and 200-series GPUs with a minimum of 256MB dedicated graphics memory.
• Experience GPU PhysX acceleration in several full games and demos today by downloading the GeForce Power Pack.
• Supports AGEIA PhysX processors and software runtimes (no change to PPU driver support).
• Includes the latest PhysX runtimes used in the latest game titles.
• Supports the following NVIDIA 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.x, 2.5.x, 2.4.x and 2.3.x
• Supports NVIDIA PhysX acceleration on GeForce via CUDA 2.0 for SDK versions 2.7.3, 2.7.2, 2.8.0 and 2.8.1 (requires graphics driver v177.81 or later).
• The PhysX control panel can be found in the Windows Start Menu under NVIDIA Corporation.
  

Products supported:

GeForce GTX 280
GeForce GTX 260
GeForce 9800 GX2
GeForce 9800 GTX+
GeForce 9800 GTX
GeForce 9800 GT
GeForce 9600 GT
GeForce 9600 GSO
GeForce 9500 GT
GeForce 9500 GS
GeForce 9400 GT
GeForce 9300 GS
GeForce 9300 GE
GeForce 8800 Ultra
GeForce 8800 GTX
GeForce 8800 GTS 512
GeForce 8800 GTS
GeForce 8800 GT
GeForce 8800 GS
GeForce 8600 GTS
GeForce 8600 GT
GeForce 8600 GS
GeForce 8500 GT
GeForce 8400 SE
GeForce 8400 GS
GeForce 8400
GeForce 8300 GS
GeForce 8300
GeForce 8200
GeForce 8100 / nForce 720a
GeForce 8100 / nForce 720a
AGEIA PhysX Processors (All)

We have an article ready explaining GeForce PhysX right here.