If you're using vista it should be fast as hell because the Aero vista UI uses directX which AO also uses (direct draw). Also you don't need 2GB of ram, you need to disable that "superfetch" service because it uses 100% of your memory to cache everything.. wtf I know.
Your statement is also void because AO uses LESS memory then windows vista's explorer.exe. Finally I think that vista is pants and I wont be using that until forced to "upgrade", XP ftw.
And if emules using too much memory then stop pirating stuff
