Ah, I assume you have it connected by HDMI?
Many Drivers assume that anything connected by HDMI is a HD TV, so they apply Underscan to it, which leads to the black edges on monitors.
Just go into the Catalyst Control Center, open "My Digital Flat Panels", then "Scaling Options". This is whereyou can tweak with the over/underscan amounts. I have mine set at 0% and it works.