Copy your entire iTunes library of music to your external. I suggest setting a folder named music, a subfolder named iTunes, and then dragging the iTunes Music folder. Go to your Music folder/iTunes and grab the iTunes Music folder and drag it into the iTunes folder you just created on your external. BTW, quit iTunes first. Then, after it has completed copying, and you may want to look at this first so you understand it, launch iTunes and go into iTunes preferences, selected the advanced tab and under general you will see iTunes music folder location. Select change and re-route it to the new location. Hit ok. Quit and relaunch iTunes. You can then play anything you need to. At this time you can also delete the iTunes Music folder from the iTunes folder on your internal drive. Make sure you don't delete the library files in the iTunes folder, nor do you need to copy them. These files contain all the other data, playlist info, etc. and they reside on your internal drive. If this is a laptop, you can disconnect your external and connect it when you are home, but remember you can't play any of your music while you are disconnected. You can however launch iTunes and use the radio stations. One last thing, make sure, though you probably already have it set to go into your preferences and under the general tab check the box that says copy files to the iTunes music folder when adding to library.