Hi there..Welcome to the Forums.!~.
There's not enough info...What sound files are u using..what extension..mp3 or otherwise..
By chance when u made your flash file..movie..did u import sound into it too..?..And are u also playing sound within the game itself..-So there's a chance it's playing at the same time..
Just a shot in the dark..
Might have something to do with sound cards too...it being Vista..a few things..start there..