the instructions are a bit iffy. download the mod and remember where you saved it. driver sweep ALL these drivers (ATI-Display, Nvidia-Chipset, Nvidia-Display, and Nvidia-PhysX) and install the 5870 driver FIRST. then download the physx driver second. then download the 8800 driver from Nvidia third. then find were you saved the driver physx mod and double click or right click open " Hybrid-PhysX-mod-1.04ff.exe ". click apply. then restart your computer.
use these steps IN ORDER. this is how i got it to work.
LOL i saw that you got it working. well ill leave this here incase someone runs into the same issue i did.