Hi All. Just bought UAKM and running it on my laptop. Seems OK but I'd like to set it to 4:3 aspect ratio and have the black bands to left and right. That is, I'd like to see circular things as circles rather than ovals. I haven't dug under the covers yet and will be grateful for pointers were to look or what to set. :)
Anyway, is this possible?

Depends on your GPU. ;)
For AMD - run AMD Catalyst Control Center > My Digital Flat Panels >Properties > Image Scaling >Enable GPU Scaling box > Maintain Aspect Ratio
For NVIDIA - run NVIDIA Control Panel > Display > Adjust desktop size and position > Scaling > Aspect Ratio
For Intel - run Intel Graphics and Media Control Panel > Display > General Settings > Scaling > Maintain Aspect Ratio

You can find your control panel/center by right-clicking anywhere on your desktop.

Thanks for the pointers! Unfortunately, for some reason my Nvidia Control Panel doesn't have the option for "adjust desktop size and position", only "adjust desktop color settings". There is a "resolution" page but no scaling/aspect ratio options.
Maybe a more recent version of the Control Panel.....

Thanks anyway though. Maybe I'll plug in a 4:3 VGA monitor and see what comes out.

A bit late to the thread, but I have to say that what I do with most DOSBOX games is open the dosbox?.conf ("?" being usually the game name), and changing the line:

fullresolution=original

To:

fullresolution=1920x1080

Put there your native resolution. It keeps the game aspect ratio.

You can also use "aspect=false" or "aspect=true". At true, it forces a 4:3 aspect ratio, and with false it keeps the 1:1 pixel aspect ratio of the original DOS games resolution, which I think is 320x200 (16:10). Some games look more correct with one option or the other.

I don't know why the GOG "Graphic Mode Setup" doesn't include a resolution option.