Troubling Question

[Jaxon]

I have recently tried playing a backed up copy of DOA2 and MDK2 self-boot games that work fine on my friends Dreamcast yet fail to boot on mine. His was manufactured in October 1999, and mine was made in August 1999. Possibly a newer hardware version between the two? Changing the game to boot off of a boot CD did work, but I would really like to know why it would work on his, but not on mine. Any help would be appreciated. Thanks

[Jaxon]

Thought i would give a little more info about this.....
Ok with Dead or Alive 2 and MDK2 when i tried using DJ it would give me the error "no seek complete"?? So i used Nero and they burned fine. Tested both games on friend's dc and they worked. On mine they did not... However games i have previously burned with DJ will work on mine... I am completely lost and any help about the no seek complete error and this new problem i have will be greatly appreciated.