To make things easy, I've already created a config file for the version of dgVoodoo used by the game to use your desktop resolution, with the 4:3 aspect ratio scaling mode.

Simply navigate to your game directory by right clicking the game in your library, clicking properties, and under the local files tab, clicking browse. Then download the dgVoodoo config file[drive.google.com] and extract it there. Your game folder should now look like this.


Now when you start up the game and press F4 to toggle fullscreen mode, the game will be pillar-boxed in your desktop resolution.

Here's a screenshot of the game at 4K:

and 1080p:


Note that this is just upscaling so your game won't look any better per se, but the reason you'll want to do this is if like me, you have a monitor that doesn't display colours correctly at lower resolutions, or stretches 4:3 resolutions.

If you're interested in how to make the config file yourself, or if you want to further tweak the settings, just grab dgVoodoo 2.54 from here[dege.freeweb.hu].

Click the add button in the top right and navigate to your game install directory. Now feel free to tweak the settings under the general and DirectX tabs and just click OK when you're done to save the config file in the game directory.