Physx?

When I installed windows 7 on my iMac, I noticed it automatically installed nVidia PHYSX control panel, along with all PHYSX engines. The thing is, I have an ATi Radeon HD 5750, and PHYSX doesn't let me toggle any hardware acceleration because of that. It'd be really nice if it was possible, for use in Mirrors Edge :3 or other PHYSX supported games. Any way to enable it or is it just a default boot camp application?