wat settings are u running ur UT3 on?? try reducing them and check. If u cant overclock ur processor, how abt overclocking ur graphics card?? if u r at 22fps, it might make a big difference and make the game playable.. Also, u need 4GB ram to run vista premium so if u can get2gb more,it wud help.
PS.. i am not saying ur h/w is bad.. but its not great either