When watching a 4x3 channel that is a widescreen letterboxed show, you will normally see a double letterbox with bars on the sides and top/bottom. The Toshiba has a zoom mode that zooms in without distorting the picture to make this fill the screen (completely fill it if it is a 16x9 show or leave small top/bottom bars if it is wider than 16x9). The Toshiba has 5 zoom/streach modes. You can look at their manual on their web site to see all the possibilities.
The bars will not harm anything except there is a possibility of burn in on the set phosphers. Keep your contrast below 50% and this will not be a problem. If you want to be extra safe, keep the contrast below 30% and use gray bars instead of black. The only burn in problems I have seen are in stores where they keep the contrast at 100% and run the set 24/7.
Rick
The bars will not harm anything except there is a possibility of burn in on the set phosphers. Keep your contrast below 50% and this will not be a problem. If you want to be extra safe, keep the contrast below 30% and use gray bars instead of black. The only burn in problems I have seen are in stores where they keep the contrast at 100% and run the set 24/7.
Rick