go to the slide where the music file is
go to CUSTOM ANIMATION
click on the "MEDIA" item
the last tab on the left should be a multimedia setting
tab, make sure you've checked the "continue show" and
entered the correct number of slides for the show ...
i don't have 98 anymore but did have, and know that
although the actual wording may appear different, you
should get the gist of what instructions should be
followed - essentially, you have to tell PPt to animate
the media object to continue playing and not pause the
show for xyz number of slides. good luck!