After you Alt+Enter - It does "window mode" your game?
If so,

1: Hover the d2r at the taskbar until the small window shows.
2: Right click that small window.
3: Choose "Maximize"
Now you'll be able to see the border, and resize the window manually using the edge of the window.

Do you see the borders doing these steps?
But you should be able to do this via the ingame settings, choose many different res sizes.

This post was edited by Yiup on May 26 2026 01:18pm