You can edit the dosboxMOM.conf file using Notepad, Wordpad or another text editor, and change the fullscreenresolution=original line to something more suited to your resolution. For example, I use 1920x1080 on my monitor. My line is then fullscreenresolution=1920x1080. (Find out your resolution by right-clicking an empty place on your desktop and choosing "properties", then the "settings" tab in Window XP. In Windows 7 you right-click an empty area of the desktop and click "Screen Resolution".
In most DOSBox games, I have the output= line set to output=overlay (I often run in window mode), but in my case this causes the fullscreen title to not fill the entire screen with these settings, so I switched the line to overlay=ddraw and it worked fine.
You can then make sure that the aspect= line in the [render] section is set to aspect=True. If it is, then it should maintain the aspect ratio that the game was originally in. You can experiment with aspect=False if you wish to see the difference.
After doing all this, you can adjust the scaler= line in the [render] section to one of the methods listed. in the description above it. Replacing whatever is on the scaler= line with say scaler=normal2x or scaler=hq2x or any of the other listed options, until you find something that suits your preference. I like hq2x or hq3x myself.
So to summarize:
- Open the dosboxMOM.conf file in the game folder using a text editor.
- Change fullresolution= to fullresolution=1920x1080 or whatever your desktop resolution is. Other examples: fullresolution=1600x1200 or fullresolution=1024x768
- Change output= to output=ddraw
- Change scaler= to scaler=hq2x or whatever you prefer.
- Save the file and try out the game.
Also, if you monitor has some sort of "auto adjust" or "auto detect" button, you can try pushing that, so it will move the screen around to fit properly. (Sometimes a monitor can forget and leave some stuff hidden.