Loading game content from external .swf files, and preloading

The other day I loaded up a game flash game (a sidescroller with an elf chick, with abuse-like controls) that I cannot remember the name of right now. At the start of that game, the preloader went through loading swf files like ‘enemies.swf’, ‘sounds.swf’, and ‘tiles.swf’. I was wondering how it would be possible to make a distributed game project like that, having the tiles seperated from the music, and the actors seperated from everything else sounds like a good way to structure everything. But, I cannot figure out how he’s doing it. Would it be duplicating movie clips from those swf files he loads, or attaching them from it’s library? Any insight you can shed on this would be greatly appreciated.