I've read that some have had issues with HD not working in a regular dvd player? But my BBC version of Planet Earth/Blue Planet doesn't say it's HD...is it all HD? Is it the discs? Sometimes they work and sometimes they don't, very frustrating.
The discs are either regular DVDs (which can be played on ANY DVD Player)... or HD-DVDs (that can only be played on an HD DVD Player) or Blu-Ray DVDs (which can only be played on a Blu-Ray DVD Player).
The discs will always tell you which type they are, but there is a clue in the price ... which is much higher for the Blu-Rays. The HDs are all ridiculously cheap now because the movie companies are no longer supporting HD.