Yes go into your skyrimprefs.ini and turn off vsync, as well as the mouseacceleration. Also, try settings shadows (and only) to high instead of ultra. And run AA and AF through nVidia control panel and not in-game.
Do you have the latest patch? If The Witcher 2 works fine it must be Skyrim itself. I have a x4 945, 560ti, and 4GB myself and the game plays buttery smooth @50fps even with mods and the major 2K texture packs installed. The patches make a difference.