GTA IV doesn't support traditional anti-aliasing. So using AA in your driver wont make a difference (and man, 32x is way too high for any modern game, go with 4x max). However, you can inject 'FXAA' into the game (Fast Approximate Anti-Aliasing). It's basically the same thing, but with much better performance and slightly less quality.
Click
HERE to download FXAA. Since GTA IV runs using DX9, copy the contents of the 'd3d9' folder into the same folder as your GTA IV exe. Tada, FXAA applied. Keep definition on