CJ let us know that the Nvidia PhysX driver changes some DLL files files within 3DMark Vantage and overwrites them with new versions. These versions cause your PPU to stop working, but will offload work to the GPU if you have a PhysX capable graphics card like GF9/GTX 200. When you install a Radeon you can't get your PPU back to work since NV overwrote the original DLLs.