It sounds like your overscan/underscan settings aren't correct. Go into Catalyst Control Center, go to the My Digital Flat Panels tab, and check the scaling options. Make sure that your overscan/underscan scale is set to 0%. Which cable are you using HDMI or DVI? DVI tends not to have scaling problems unlike HDMI. If you are using HDMI and you have a DVI cable, try using that.
I did use an HDMI, so thats the culprit?