Many of the ATI control panels have methods to tweak the output. Be sure to learn how to clone your desktop display as well as "Extend my desktop". Many fumble this area of Windows so keep at it.
I have a PC running Windows 7 in my home theater through a Panasonic PT-AE2000U projector. I have an ATI Radeon 5770 graphics card with the latest Catalyst drivers. The screen resolution is set to 1920x1080. The problem is that the image displayed to the screen doesn't fill the entire screen. There is a black border around the entire screen of 5 inches on the sides and 3 inches on the top/bottom. The projector is perfectly calibrated to fill the screen using my Directv reciever and Playstation 3.
Any ideas on how to fix this?