[SPOILER="Spoiler"]
[Image: http://i.minus.com/ikfs8UEsw72zB.png]
[/SPOILER]I uninstalled physx through control panel, now when I go to install it, it fails.
To uninstall physx and then re-install it you may as well remove all the nvidia drivers and then update them (or re-install the latest if you already have them).
You might be getting an error when trying to re-install because the rest of the nvidia stuff is still there.
I think the installer allows you to select just physx or other components but I wouldn't trust it. Also be sure to reboot after each step.
which nVidia card do you have as not all support PhysX for your driver problem and for your steam problem have you tried shutting down steam then running mabi ?