If you have /r_fullscreen 1 and the correct resolution and r_mode, you should check your graphics card driver settings. Actually I don't know if it's normal on Windows to have ET in windowed mode without decoration (title bar, etc), I've used Linux for so long that I forgot.
First of all, type /r_fullscreen and see what value it says, if it's 1 or 0
the same for r_mode (and custom resolution) - btw, customaspect is ignored in ET afaik (at least it is in the standard ET 2.60b don't know if etlegacy uses it , but not ET)
check if it says 'latched' or not in some settings.
If you really are in the correct mode, then it could be some driver issue imho
you don't need to check your configs or stuff, first of all open the console and check if the resolution in ET is correct, as I told you, if it is then the problem is not Et and it's useless to reinstall or change configs and such drastic things because you won't solve anything
Edited by SunLight, 24 July 2015 - 11:49 AM.