The manual only says to push the '*' button to change the picture size. I tried this when I first got the receiver a few weeks ago and found 4 or 5 different options. However, I'm finding now that it doesn't always work. Sometimes I only have the option to switch between normal and full zoom, other times the display changes indicating gray bars or partial stretch, etc., but it doesn't do anything to the picture. I have adjusted the position of my HDTV picture in the menus, does this affect this feature? Can someone post when you can use the '*' button and what options are available for which formats?