I have a laptop with a 1280x800 native res monitor and an ATI Mobility Radeon X300. On there if you go to the Display window, then Settings, then Advanced, you can click on the Displays tab, hit the button for the laptop’s monitor, and disable scaling. You can also tell it to scale, but keep the aspect ratio correct.
I turn off scaling because the best non-widescreen res I can do on it is 1024x768, and when it scales it up from 768 height to 800 with the smoothing text and thin lines look terrible. (But for low res games like Starcraft I have to turn the scaling back on).
With scaling off there is a thin black bar on the top and bottom of the screen as well but it’s not too noticeable and everything else is crystal clear.
I don’t know for sure, but I would guess there are similar settings for other ATI based laptop vid hardware.