I have a DVD VHS combo player and recorder. I frequently record DVDs of programs I watch on TV and they play back just fine. However, if I try to play the same DVD on another machine it is not recognized. Am I missing some trick or is there some format issue I do not understand? Thanks

It could be designed into your player. It was probably required so people don't make copies of shows and sell or distribute

Some dvds have to be finalized on the dvd recorder you recorded the show on. On mine, finalize is accessed through setup. That is supposed to make the recorded dvd compatible with other players.