Screen Stretched off desktop

Sorry if this topic has already been discussed, but I just built a new pc and my monitor is connected w/a DVI 2 HDMI cable. I first noticed this problem whenever I would install a new game and the game resolution was not automatically set to my monitor native resolution, when i would exit game I would notice that my desktop was slightly stretched off screen. Then i upgraded vid. drivers and then it was always stretched off the screen no matter what. Finally I just connected the plain regular 'ol d-sub cable and it has fixed the problem but i don't like the quality over dvi 2 hdmi. With my old system that had a 8800 GTS 640mb card, it worked fine using the exact same cable, so why will it not work now?