HD display question

[LT9000]

Finally got an HDTV, the Sony V3000 in 46 inches. Newbie question: Sometimes when viewing what the TV says is HD content, their will be black bars at the side. The TV calls it 1080i HD. So are some HD broadcasts with the black bars on the sides? What's likely going on there?

(Some other times I get HD in 16 X 9, like with Lettermen or O'Brien.)

[jagabo]

A lot of what's broadcast on HD channels is 4:3, often just upscaled standard definition material. When that happens you get black pillarbox bars on the sides.