I have this old game called Port Royale 2. I've been playing it for years on a 1920 x 1080 display, but the game is old so I played it with a lower resolution, but it was still quite enjoyanle since that resolution had only 2 small black borders on the sides. A month ago my operating system (Windows 10) was restored to solve some software problems. I had to reinstall all the games, but now Port Royale 2 is opened on a way smaller resolution (1024 x 768), making it unplayable because of the huge black borders and the small view. There is no ingame option to change the resolution. Also, I have the same issue on another old game from the same producers (Imperium), which makes me think it may be a Windows 10 problem, and not a game's one

If I recall correctly, GOG patched it to use their internal DX wrapper. If that's the case, there should be a "dxcfg.exe" file you can run and set multiple options, including your preferred resolution and aspect ratio.

The game's resolution is limited to 1024x768. To get rid of the black borders is only possible
by stretching the game without aspect ratio correctness.

I have the dotemu version of the game. There is a config file called PR2Config.exe.
If you disable "Execute in Fullcreen Mode", the borders are gone.

Thank you for helping! I can't tell if your tip worked since i don't have my pc with me these days, but I will as soon as possible

Try selecting "desktop resolution" and "correct aspect ratio" into te dxwrapper configurator. The maximum vanilla resolution was 1024x768 but the wrapper config use to override the game's res.
In 3D games it works fine showing the game at your desktop res and mantaining the 2d parts size (GUI, fonts etc...) at the game's internal resolution.

I remember that PR2 has mixed graphics, real 3d and 2D, so I am not sure how it will work exactly in this game. But it is worth the try