As the title says I'm looking if there's is a possibility to change the aspect ratio of my display.

The thing is my native aspect ratio is 16:9 with a resolution of 1366x768. However I'm currently trying to play a pretty old game with maximum resolution of 800x600 (it's Diablo 2) and whenever that happens the aspect ratio changes to 4:3 and since the the resolution and aspect ratio don't match I end up having two big black lines at both sides of the screen.

I know I will lose some image quality but I want to try it, so could somebody please tell me how to change it please?

I have an Intel GPU, if anybody asks.

PS:If anybody knows how to change aspect radio when using the game alone that would be wonderful.