I would highly recommend upgrading your graphics card because although you may be able to run the guy with bare minimum settings and low resolution, it's not going to be that great of an experience because the game will stutter and without all the bells and whistles you get with the higher settings, the game is not going to look very good.
If you don't want to break the bank but still have pretty decent performance at high settings, I would maybe look into the new Nvidia GeForce GTX 660 which should be around $230 although I'm not sure its available yet. The 660 isn't absolutely neccessary and I'm sure you could find a cheaper solution closer to $100 that will run BF3 fine but your cpu is rather weak so every little bit helps.
Well I managed to run it at a very unstable 60 fps, which dropped down to 30 and sometimes around 10 on my 9500 GT. Obviously I have a new card though now . Its playable, but when you go to fight enemies at a range, at 480p all you'll see is pixels.