What version of the driver are you running? If you are running the 2x.xx drivers, anti-aliasing settings for Direct3d and OpenGL are on the same page. Under Additional properties, there is a tab called "3D Antialiasing settings". If you have drivers older than this, under the OpenGL settings there should be additional settings you can click on that will let you adjust the antialiasing settings. The older drivers you were able to set the antialiasing settings separately for Direct3d and Opengl.