its automatically kept at 1280 by 1024 and i cant change it?

Try something else than Fullscreen windowed.

already did

go to options and change it there

Go to options > put it in fullscreen > change resolution

What's your desktop resolution?

If playing in windowed mode, resize the window as you normally would - click and drag bottom right corner.

Otherwise you must play in full screen to change resolution.

Buy new PC

Same with me, I play in fullscreen windowed, my desktop resolution is 1920x1200 but in D2 its 1280x800 (16:10 widescreen) and can't be changed

/e: Changed to fullscreen, swapped to 1920x1200 and changed back to fullscreen windowed and now it locked at 1920x1200. So it's all good

This post was edited by Erlend on Jun 11 2012 02:12am

You have to edit "d3prefs.txt"
You will find it in "My documents -> Diablo III"
You can change the windowed mode resolution there