Witcher 2 is a very heavy game when it comes to graphics. STILL, there are out there some configurators (custom and probably with virus) that can give you a better settings with still "ok" frame rate. So if you are willing to risk them, you might get a better looking game.

As far as i know 2.0 patch introduced a bit of tweaking and a bit more effective settings for the engine, so have you tried patching it?

And as everyone said, "dont overclock" its becouse even if your overclock wont risk your gpu, it wont give you a decent improvemnet (540M is not a strong GPU, so you would need a crazy oc to get a decent improvemnt).