sear: The game supports anti-aliasing by default, specifically MLAA, which provides very good quality at virtually no performance cost. Have you tried enabling that in the game's config program?

sear: The game uses a custom anti-aliasing solution which does not have degrees in the same way MSAA (multisampling) does. MLAA is a shader-based effect and not "true" anti-aliasing, but it produces very reasonable edge smoothing at a fraction of the cost.

If you wish to use MSAA, supersampling or transparency AA then you should use the config program in the game's directory to disable anti-aliasing in-game and use your video card's driver control panel to force anti-aliasing instead.

There is a chance, however, that MSAA and other methods are as of yet incompatible with The Witcher 2. This may change when new video drivers are released by AMD and NVIDIA. Also note that The Witcher 2 is a DirectX 9 game, and it's possible some of the game's graphical effects are incompatible with traditional MSAA (a limitation not found in DirectX 11), so it may be impossible to use any other form of anti-aliasing unless CD Projekt patch DirectX 11 support in. I have yet to test this, and be warned that it might cause the game to run significantly worse.