The version 9.09.0428 of NVIDIA PhysX System Software is available. This version is WHQL certified, woks for Windows XP, Windows Vista and Windows 7, and brings a small change only (fixes version number reporting conflict) compared to the last release (9.09.0408).
You can download it here: PhysX System Software 9.09.0428.
If you have a GeForce 8/9/GT200 you can enjoy the hardware acceleration of PhysX. But PhysX runs also in software mode with all other cards (GeForce 5/6/7, Radeon, S3 Graphics, Intel, …).