The aspect ratio (4:3 480i,16:9 1080i, etc.) is changeable via the 'Video Settings' sub menu that is accessible if you press [STB] and then [MENU]. Look for it under the 'Settings' menu item. If the display becomes distorted or does not display at all, the TV does not support the aspect ratio/display combination, and you can opt out by pressing the [OK] button, as this will revert to the previous settings.
It is also accessible via the internal menu that can be accessed by powering off the STB and pressing the SELECT button several times until the menu appears. When changing it there, however, the change is not immediately reversible like it is in the method above. If your display becomes distorted, you may have to make several other keypresses at the STB to reverse the change.
Hope this helps.
Written by Ken Yee - John L
Last updated on 11.15.07