I don't know if this is any help because I haven't got a mac PC, but
try press the F10 key until the sound increases, if this doesn't work
then I am sorry but the only thing I can think off is going into the
properties of sound and see if it is anything there or follow these
instructions:
> Tools
> Options
> DVD
> Advanced.....
and continue with the volume their!
Hope that is any help to you! Good luck!
>> Stay informed about: no sound