I know fullscreen mode it’s just a non border window big like the monitor…
I just want to know how to change display mode. Do I have to use ChangeDisplaySettings or there is something better?

and this is not an opengl question:
when starting my app I show a dialog with a combo from where the user choses disp mode.
I manually insert list entries via resource editor but when i click on the combo it is empty… (

You have to use ChangeDisplaySettings, or you can use a toolit that does it for you. My suggestion is GLFW: http://hem.passagen.se/opengl/glfw/

It does the magic for you, plus some other neat things too. Plus: it works just as well under e.g. Linux .

If you don’t like to use GLFW, you can look at or use the source code for fullscreen windows (you’ll probably find that it is not as easy as one would think).