Samsung monitor suddenly not displaying on full screen

[StRaNgEdAyS]

Brand new system, Samsung S24B300 on PowerColor HD7970 ATI card via HDMI was working fine last night, booted this morning with a 15-20mm border between the desktop and edge of screen area.
If I reduce the resolution to 1600x900 it fills the screen but at the recommended 1920x1080 it will not stretch to fit the screen.
I've updated my drivers to no avail.

 

[MongoSmash]

Go into Catalyst Control Center and turn your Underscan/Overscan to 0.

 

[StRaNgEdAyS]

Thank you very much!
I'm perplexed as to how it changed overnight, but that fixed it!