I'm sure this has probably been asked before but, all of my dosbox games run in widescreen and i can't figure out how to change it. I've been messing with the Dosbox configurator but nothing seems to work. My AMD settings are set at preserve aspect ratio. Games like MMVI run fine in the correct aspect ratio, but when I play MMIII it's stretched out to full screen 1080.

There should be a checkbox for keeping aspect ratio in the configurator, if not edit the specific .conf in the game installation folder and search for the line keep aspect=false and make it true.
Also use fullresolution=desktop and video output=overlay or ddraw.