Such issue occurs when the native screen resolution is in vertical aspect ratio (portrait mode), with height resolution parameter being much bigger then width parameter. This is a problem for older games, which does not support screen rotate function.
Depending on the game the the solutions will be different. The easiest way would be to try to run the game in windowed mode. If the game starts with options launcher, you might be able to enable windowed mode there. If not, sometimes simple key combination Left Alt + Enter will switch the game's resolution to windowed mode.
A) If the game is a DOSBox title, you can enable windowed mode by either pressing Left Alt + Enter, or by following the below:
Please run DOSBox Graphics Mode Setup:
- If the game was installed via Galaxy, please select the game in GOG GALAXY, click on Customize -> Additional Executables -> Graphics Mode Setup
- If the game was installed via offline installer, then open Start Menu\Programs\GAME-TITLE\Tools\Graphics Mode Setup
In Graphics Mode Setup tool please select:
Graphics Mode: OpenGL
Fullscreen: Unchecked
Go to Advanced Options.
Windowed Mode: Select 1280x720, or resolution closer to your display resolution.
Press Save and close. Now try to run the game.
B) If the game is an older 2D title, using DirectDraw, you can try to use this DDwrapper:
http://bitpatch.com/ddwrapper.html
Once ddwrapper.zip will be downloaded, extract ddraw.dll and aqrit.cfg from the package and paste the files to the game's installation folder, where the game's executable is.
C) If the game is an older 3D title, you might want to use dgVooDoo 2 wrapper:
http://dege.freeweb.hu/
After downloading extract the archive. Open it and go to MS folder. Inside you should be able to find:
D3D8.dll
D3DImm.dll
DDraw.dll
Copy all three files to game installation folder, where the game's executable is.
D) If these will not help, you can also try to use DxWnd to try to force the game to run in windowed mode, even if it's natively doesn't have such option:
https://sourceforge.net/projects/dxwnd/
This guide on Play-Old-Games website should be handy in preparing DxWnd:
https://www.play-old-pc-games.com/compatibility-tools/using-dxwnd/
E) Finally, some games might have a different solution or have such issue resolved with a community patch/mod. We strongly recommend checking PC Gaming Wiki in case if you did not found a solution above:
https://www.pcgamingwiki.com/