Just thought I'd add my findings.
I submitted a ticket to ATI asking about scaling while maintaining a 4:3 aspect ratio and here's the response:
"I'm sorry but this is a feature that is not support by our drivers.
You can provide feedback so that we can encorporate that feature into our drivers."
So I went ahead and left feedback. If any ATI users want to leave feedback you can
here.
I went ahead and left feedback with them, and pointed them to this site and specifically this thread.
I know some folks here prefer nVidia over ATI but I've really like the ATI card simply because their DirectX support is better, especially if you are running older DirectX titles. For example, older Unreal-engine games seem to run better on an ATI card, at least in my experience.
ATI cards do have one mode (Use centered timings) that allows you to black box a game but you have to be using DVI and only certain resolutions work. In fact, the only resolution so far that seems to work and maintain a 4:3 aspect is 1280x960. So running Warcraft III works in that resolution and maintains the aspect ratio but it doesn't actually scale to fit vertically, it actually has a black box on the sides and the top and bottom. With my screen (1680x1050) its not so bad because the black on top and bottom is <100 pixels. If I run any other rez tho (800x600, 1024x768, 1280x1024) it seems to ignore the center timings setting and stretches to full screen.