You are a little worse off than I am. I'm playing on lowish settings right now with a P4 1.7GHz, 768MB RAM and a 9600 Pro. It's slow enough that I'm noticing some stuttering, however it hasn't really diminished my enjoyment of the game so far, probably because I'm used to the stuttering from other games.
If you lower everything down to the bare minimum you should be able to play the game. You may have really poor looking characters and have to run at 800x600, but I would think that you could possibly do it depending on what your tolerances are.