Windows 7 Black border when Computer is Hooked up to TV

I have a multimedia box hooked up to my TV. It's a Shuttle X38P2-Pro With a 2.5 Ghz Wolfdale Processor and a Radeon HD 4770. The TV is a Samsung plasma, and the native resolution is 1024x768, but it streaches everything if I use the native resolution, so I set it to 720p (the ostensible resolution of the screen when it was sold to me). when I use this resolution on the Ubuntu installation, it will run from edge to edge of the screen. However, when I run this resolution on the Windows 7 installation, it has a black border around the video. I believe I have installed the most recent driver for the graphics card, but I can't find a solution for this. Does anyone have a suggestion?