PC Games help

heloo guys, tday i installed scarface: the world is yours. but when i started to play the game started at very low speed. i also installed game accelaretor but nothing changed. my computer has sufficeint space and proper requirements- windows xp amd athlon 64x2, dual core processor 4000+ 2.09 ghz, 1gb ram, ati raedon xpress 1250. so now what to do