HELP! I have a DVD reel that is saved onto the hard drive of my computer, I've tried three different kinds of DVD media, different burning speeds, but after I burn the DVD-R on my 13" G4 --> The DVD plays on my stand-alone DVD player, but when I put it into my 13" G4 or my friend's ibook, it says "unsupported disc" -- HELP! WHAT AM I DOING WRONG?