Report "Gtv14t5dvd when connected to a freeview "digi box" the screen aspect changed from a full screen picture to a wide black strip at the top and bottom of the picture i e letterbox aspect. i have the instructional manuel but there is no mention of changing the aspect or how to make the picture height fill the screen or "stretch the picture vertically can you help with this., also it plays cds ok but when i put a dvd in the screen says no disc and wont play?"