HDTV question

The broadcast channels - ABC, NBC, CBS, FOX, etc. - are exactly what you see in "standard definition." They switch back and forth between standard definition and high definition as needed for either the programs or commercials.

TNT HD is all HD, but other than that, it's exactly the same as what you see on the standard TNT channel... they just "up-convert" and crop/zoom as necessary. Other than that, the commercials and programs you see on TNT are the commercials and programs I see on TNT HD.

Universal HD and Discovery HD Theater are very limited commercials, but they do have some. Both Universal HD and Discovery HD will "up-convert" the resolution as needed, but will leave the commercial in it's original aspect ratio.

InHD and HDnet are commercial free, I believe.... don't watch them enough to remember.