Dude BF2 is a hog, I agree. With the way it seems, it's like you need a Super Computer to play that damn game.
Don't understand why people say this....was made to be less demanding then BF1942 and doesn't seem to be a hog at all..
Alex's computer is better than mine and I can play that gamed Maxed out easily...granted I run it at 1024x768 resolution though just for smoothness headroom....so if you're doing like 1600x1200 or something insane like that you should turn it down.
Your AGP aperture should be fine at 128mb, if it's less than that you might consider turning it up...
Other than that it's not your hardware that's causing slowdown....it's gotta be all software related.
If you have the latest forceware drivers you might try using the 77.30's that came with the BF2 demo (also available at guru3d.com ) as I've heard a lot of people experience issues with the latest forceware