Try a program called 'Smartclose' [takes off all background processes and then enables them all again after you've played]
Also try an old Ati driver. Mine was running pretty poorly on the Catalyst 5.9's but then I changed back to 5.6 and it plays fantastic now.
Search through the
http://www.totalbf2.com forums, check the stickies, they help alot.
As said tho, you need at least another 512mb of Ram. If poss go for 2gb but an extra 512mb should make a difference either way.