magic, i have 2 gig of ram and a 512 mb vid card, BUT i had the same res on 1gb ram and a 128mb vid card, although the game wasn't quite as purty.
i use the ATI control panel stuff which does some really nice things.
i think i run 6X anti-aliasing, 16X advanced anisotropic filtering, high quality mipmapping etc.
BUT, the thing that gives you the high resolution is the high res graphics pack that you download seperate from the game. DL it and install, then change max tex size to 1024 in the video setting at the main menu, the game looks so much nicer.