For the launch of Mafia II demo, NVIDIA has released of new official PhysX driver. This driver fixes a bug that prevented PhysX from being accelerated on Optimus PCs. There are also some bug fixes for Mafia 2 (more technical details about PhysX and Mafia II are available HERE).
You can download PhysX 9.10.0513 system software HERE.
You can quickly test the PhysX support thanks to FluidMark