While Hylke isn't right, most needed ever will be 2 GB of RAM. NO ONE will need 4GB + 512MB of RAM. My LAPTOP has 1 GB of ram, and I can run Firefox (takes alot more RAM than IE), Freelancer, EVE, Skype, Teamspeak, Xfire, AIM, MSN, Utorrent, FAM, and Itunes all at the same time.. Thats with 1 GB of RAM. Frame rate drops about 2 per second. Thats not that much. Thats what FREELANCER and EVE going..
BFH, you should be watching your processor speed. If you have 4GB RAM on there, than its your processor speed thats slowing you down, as 4GB of RAM would run BF2142, BF2, and BF1942 all at the same time..