It all depends on the number of vertical lines. On a CRT display it doesn't
matter how big the screen that is projected by the guns is, the phosphors will
be lit where they get hit - hence you can display 640x480, 640x400, etc in the
same vertical sized screen, the pixels are in no fixed position on the front of
the display On a LCD display such as your Aero, there is only 480 vertical
lines of display, and each pixel is fixed - you can't display 400 lines over
the whole of the vertical screen without some rows becoming 2 physical lines,
which would be a hassle to implement and would look terrible. The result is
that when you use other than a complete multiple of 480 vertical scan lines
then it displays it on only 400 or so of them, and centres those used
vertically, resulting int what you were describing. In my travels, I've found
that either one of 43 (EGA) or 50 (VGA) vertical lines have produced a full
screen of text... try one of those.