HDMI Input Not Filling Monitor In Applications

I've just built a new computer with Windows 7 and a gigabyte brand radeon HD4890 and have been having the same issue as some other users with regard to the over/underscan.

I managed to correct the inch or so of unfilled space when displaying the desktop by using the under/overscan utility in CCC (thanks to info on this forum ^_^) but found that the problem still exists when I ran my first full-screen applications.

I installed, updated, and ran Spore: Galactic Adventures to take a look at how my system was going to handle everything, but found that the dreaded inch was back. The really odd thing was that when I switched Spore to windowed mode, the inch had gone and I could maximise to full-screen. Of course, the window header and taskbar kind of detract from the game, but this isn't necessarily an issue for Spore (which can hardly be described as immersive).

I am, however, concerned that this issue may pop up in other games where the window header and taskbar will detract from the game (if it operates well in windowed mode at all).

I plan on investigating further later today, possibly in the direction of motherboard and chipset drivers, but also testing with other games.