Lg Non-hd Channels Blurry Is There Something Wrong With My HDTV?

Is there something wrong with my HDTV? - lg non-hd channels blurry

OK, so just bought a plasma 50 "720p LG. When we arrived, we had Dish Network. And they wanted to sign another 2 year contract, so that we can use HD programming. So we've got Comcast HD DVR. Now blurred the picture on HD channels perfectly, but a little. And when I press guide, the little box that shows look better on the top right of the list of channels, as if the driver is off. In other words, the image even better if it is smaller. So I was wondering whether there's a way to change the configuration of the image so it looks like he is not on the line, instead of showing how a smaller picture? In addition, the HD channels are no better on an SDTV.