First of all, I'd like to say that I love this game. I've been having issues with my frame rate, mostly in battle. It's been tolerable up until my first dragon fight. The fps shot down horribly low. I would like to keep anti-aliasing up at 2x, and I've seen many recommendations to disable the AA settings through Skyrim and turn them on through my graphics card's settings. In attempting to do so, I've found that I am unable to turn AA on through the Nvidia control panel. Anisotropic filtering works fine, however. Is there a reason for this or am I doing something wrong?

Screenshot: http://i40.tinypic.com/xp33sw.png

My card is Nvidia Geforce 9100.

Set "Antialiasing - Mode" to either Override or Enhance, and the option to change AA will be enabled.

EDIT: Although, something that will give you better performance with similar visuals, is turning on "FXAA" in the Advanced section of the Skyrim options, and leaving antialiasing off completely.

With a video card like the Geforce 9100 id recommend turning off AA. AA is a very demanding feature and your video card doesnt really have the horsepower to do AA without lagging im afraid. Id say your better off with FXAA instead of real AA. FXAA looks good, doesnt have an Fps hit (AA solution designd for consoles, coded not to be powerhungry on the GPU because console GPU's are weak) , only downside to it is that itl blur textures abit, thats because its what it does, instead of straightening the edges like other AA solutions do, this blurs the edges instead to make the jaggyness less noticeable, and it works great actually so try that out.

That card is struggling... why would you want to reduce performance more-so by enabling AA?

To answer your answer, have you tried enabling the AA - mode option first?