Boxeo

1inxs

I think you're referring to the letterboxing. You will sometimes see black at the top/bottom of the screen. If this is what you're asking, it is totally normal and will not effect your TV set. The following link gives a detailed answer.
Letterbox - Wikipedia, the free encyclopedia

DTVuser2009

sometimes the box won't allow you to get rid of them and say 'aspect ratio cannot be changed on this channel' and if you are using a 4:3 standard TV, you can set the box to 16:9 widescreen and try zoom again, and it works.

Same if you have a 16:9 widescreen with the same problem, set the box for 4:3 standard and zoom again. for some reason boxes won't zoom an existing 4:3 broadcast if you're currently set at 4:3 or vice versa for widescreen. why i do not know.