theres not problem. what you are seeing is 4x3 content. your tv puts the black bars on the sides to keep the aspect ratio, so people dont look extremely fat on the screen. if you tune to an HD channel, you will find they will usually go away, unless the station is broadcasting a 4x3 show on their 16x9 channel.
if you really want to get rid of the bars, which i would suggest not doing because it stretches the picture, you can use the tv's remote, and look for a "wide" or "aspect ratio" button, and keep hitting it until the picture is stretched.