these people are not entirely correct by saying that the bars are dictated by the hd signal, if you are watching an hd program (formatted 16:9) on a traditional 4:3 (hd) tv then you will always experience bars on top and bottom unless you zoom in. this is because hd tv is widescreen and to maintain aspect ratios the image is made smaller so that it can fit entirely inside the screen in relation to width only. the color of the bars WHEN WATCHING HDTV is dictated by your tv not the program. the signal is broadcast in 16:9 with no bars on top and bottom at all, when that signal enters your tv depending on your tvs ratio the picture gets adjusted. sometimes tv manufacturers allow you to change the bar color. ANY COLOR OF BAR AT ALL ON YOUR TV, PARTICULARLY PROJECTION TVS, WILL CAUSE "SCREEN BURN". BLACK BEING WORSE THAN GREY FOR "SCREEN BURN".

what you experience on dvds is slightly different. if you are watching a widescreen movie, it is likely not in hd standard widescreen (animateds usually are, and more and more are close enough). the movie could be recorded in 2.35:1,1.85:1, etc. aspect ratios which are not 1.78:1 which is the hd standard ratio. if you have a widescreen hdtv (16:9), when watching wider formats, i.e. 2.35, you will see black bars on the top of the picture for the same reasons why you do on hdtv programs (to preserve aspect ratio). these bars are dictated and recorded on the dvd. so if you have a 4:3 and are watching a widescreen movie you will have even more bars. on a 4:3 tv, when watching a widescreen dvd you could actually have black bars governed by the movie to fill up your tvs "widescreen" space, and then also black or grey bars on the top and bottom that are from the tv filling up the not widescreen space. I WILL REPEAT THAT ANY BAR OF ANY COLOR OR LOGO OR STOCK TICKER WILL BURN YOUR TV, AND IF YOU HAVE PROJECTION IT WILL BURN IT MUCH MUCH MUCH FASTER, BLACK IS THE WORST SINCE IT IS A COMBINATION OF EVERY COLOR... i hope this is clear enough... there is more to the bars than what i have just said, but i am only trying to answer your question...