<F11>, 'theater mode' is different from choosing full screen. However, Word doesn't process <F11>.Pressing F11 in most Microsoft products will do this for you. I don't know if that's different from choosing full screen through the menu, however.
I am trying to make a document wider, so that it fills the entire screen without the gray edges as such:
This is in View>Full Screen on a Word document.
Appears like this with text or pics.
Margin alterations does not seem to help.
Maybe a winxp setting?