Apparently since the 186 GeForce drivers, Nvidia has disabled PhysX processing if an AMD video card is being used for the graphics processing. That is just not cool at all. I agree with Unknown-One's statement, "Ok, so don't support it, but don't go out of your way to disable it!". If this was my decision, I would make sure that PhysX works very well in this configuration so that the user can see the value in my company's technology. Perhaps then the user might be presuaded to buy a video card from Nvidia the next time around. What do you guys think?
Here is Nvidia’s customer care center entry about this situation:
Nvidia supports GPU accelerated Physx on NVIDIA GPUs while using NVIDIA GPUs for graphics. NVIDIA performs extensive Engineering, Development, and QA work that makes Physx a great experience for customers. For a variety of reasons - some development expense some quality assurance and some business reasons NVIDIA will not support GPU accelerated Physx with NVIDIA GPUs while GPU rendering is happening on non- NVIDIA GPUs.