VSE output not going full screen I am still noob, following tutorials, but i can copy and paste like a pro, that said, here is my problem:

In VSE, i set dimensions to 1280x720, a lot of my clips are 1920x1080 (or 4x3 ratio), and as i animate, i get video that is 1280x720, but when i go full screen, video is centered in the middle of screen (my monitor is 1920x1080).
I tried add->effect strip->modify but still same results...

is there a setting i missed, miss clicked,
or do i have to convert all my clips to 1280x720 first, before importing them to blender...?

I am using 2.78 version of blender.

Thank you.
As it turns out, blender is just fine, and the problem was in mplayer, something that or other, xv, x11 thingy... i took videos on other machines (linux and windows) and files were working just fine in full screen. So i went after mplayer, and there was this update that required restart of X11...

anyway, i am sorry i took your time, noobs like me are probably the worst kind...