How to center image on widescreen LCD with Radeon HD2900 XT?

So I just assembled my new PC today. It's awesome. Liquid smooth graphics and everything, except an annoying problem..

I have a 20.1" widescreen LCD monitor with an aspect ratio of 16:10. This is hooked up to a HIS Radeon HD2900 XT 512MB GDDR3 video card via a DVI-D cable. In games like Halo, which max out at 1280x1024, the image is distorted, stretched horizontally. I would prefer that the image is displayed centered in the normal 4:3 aspect with black bars at the edges. I enabled the "Use centered timings" option in the Catalyst Control Center, but it makes no difference, except on a 1154 by something resolution, but even in that the image is stretched horizontally.

I'm pretty sure this is a common problem with a common fix, so please help. Thanks!

if you have any settings monitor side you will need to adjust those too. that is how it is with me. i need to telll it to stretch, maintain aspect ration or use 1:1pixles.

however, funny thing is i have tried games at 12 x 10 full panel like oblivon and it looks fine. although i run games at 19 x 12 i like to see how they look at lower res. although not as nice i find that most games look fine at lower ones especially with tons of AA enabled.

not quite true. the gfx card is the one that decides which resolution it is. yes, a monitor can have scaling options but so does the gfx card.

centred timings means it will centre the desktop regardless of if it is the same size as the panel. or so the CCC says.

however, i believe it is the monitor that has the final say in it as it were but the gfx card and the monitor should be set the same to ensure the best results.