Well, one way of fixing this can be to watch the files sync to your mp3 player and when it starts syncing the unwanted files, just simply press "stop sync". I think i know what you are using and i had the same problem at first. you will make a sync list and click sync but after that list if finished, it will sync the rest of the songs from your computer also, you can just wait for your wanted sync list to be finished and as soon as it begins to sync the unwanted media, just press stop. this wont harm your computer or your mp3 player.