If you don't want to download third party software, you can enable your iPod for disk use by plugging it into iTunes and going to "iPod Preferences" , plug it into the computer you want the songs from, cancel anything iTunes tries to do, create a folder in your iPod using My Computer, copy the songs from their location on the computer to the folder you created on your iPod, plug it in on the computer that has the library that your iPod is linked to and copy the songs from the folder you created on your iPod to your iTunes music library. Then, open iTunes and select "add folder to library." Find the folder the song(s) are in and select that folder. Your computer should add those songs to your library and your iPod. It is less complicated than it sounds.