UPDATE: Setup: Windows 7 x64 (build 7100) , 4870x2 + 8800gts 1) Update (via Windows Update) to the latest WDDM 1.1 nVidia driver - reboot 2) Install latest Catalyst Suite (9.4 now) - reboot 3) Install latest PhysX driver from nVidia (9.09.0408) - reboot I've checked Fluidmark benchmark and nVidia Nurien Tech Demo: both PhysX hardware enabled. No need (for me) to mess with primary/secondary adapter or enabling/disabling ATI to setup PhysX. Remember: DON'T install nVidia graphic driver from their site. Use Windows Update. Things NOT working: PhysX control panel doesn't show up. I'll check later some games to see if PhysX is working properly.