My games only let me go up to 1600 x 900 and my friend are able to go to 1680 x 1050 res and thats what my res

ASUS M2N sli delux, AMD 64 X2 5200 OC to 2.9 2 Geforce 7950 GT KOs sli 4GB corsair Memory. This is on all games COD4, Halo2, crysis, every game Sceptre 20" 1080p model LCD ALL Drivers and firmware for all hardware is updated and i can't figure it out!