Here's what I did. Use revo uninstaller & remove Ageia. When that's done,make sure that Ageia is deleted from program files. Then, go to start, run, and "regedit". In the registry editor, go HKEY --->Local Machine--->Software & then delete the Ageia Physx key. When that is done, you can then install whichever older version you like. I tried everything else, but this one really worx.