sound problem on dvd player

Hi,

I am doing my first dvd and have a problem with the sound when the dvd plays back on domestic dvd player. The dvd is built with one main menu page and a button which open a slideshow (m2v) with a music (dolby). With the simulator mode on dvd studio pro 4 everything is fine but when playing on different dvd player the sound sometimes appears or doesn?t.
What worry me is that when the disc is formatted I got info that the disc has copyright material: I did prepare the slideshow and the music has been composed by a friend. Is there a way to find out with dvd studio pro, which material is copyright protected.
It will be very keen of you to help me to solve this problem which turns me mad.
Thank you,

Sandrine