Alot of times the song's are in Mp3 format when you download them, but if you try to play them in Windows Media Player it will pop up a window saying "The file you are trying to play is in another format than listed" and it will ask you do you still want to play it. If it pop ups that means your Ipod can't use it. Because in your IpoD it will be an error , instead of automatically choosing yes. So check all of your files before your upload them to your IpoD.