I cannot stand the black bars anymore

Hello everybody
I have played crossfire on my old pc for over 2 years now and now i bought a new laptop and all..
so i thaught, better graphics faster gamplay and so on...
But when i installed it and played it i get these big black bars on the side
My desktop resoltion is 1600x900 and if i play games i play them in 1280x720
so i whas thinking no problem i just change the resolution..
then i get this strange error message that my screen does not support that resolution (there isn't even a 1280x720 res in 16:9 aspect ratio ) so now i have to play like it is in this damn 800x600 resolution and i find it annoying and not playable... someone plz help me i have searched the whole damn forum for a solution.. NOTE: i have an ati video card and it's set on 1600x900 as i said before..

thx in advance