Whether you use WMP to ‘sync’ or drag & drop music files, you determine where they are to be stored, in the internal memory or external memory card. They are 2 separate memory storage areas, although your Fuze will populate its lists (Artists, Albums, Genres, etc.) from both sources and display them as one. Your Fuze will also play music from either location as if there is no difference.
Quite the smart little cookie, huh? You can even load up the card and leave the players’ memory empty in you want. It doesn’t care. 
