Hey M8,
All depends on the aspect ratio, i thought i was going barmy when i first purchased my W/screen panny
The aspect ratio 1.77:1 is your 16.9 or w/screen which will play full screen, then you have the letterbox versions that will play with the upper and lower lines. The next aspect ratio tends to be 1.85:1 which again should play at full screen. The biggest will be 2.35:1 or Cinemascope- more DVD`s have this these days so you are gonna have the lines as it needs to lessen the height to ensure the correct ratio to the width.