Apple's iTunes software manages the library of music stored on your computer and handles synchronisation with Apple's portable devices such as iPods and iPhones. On occasion, you may want to transfer one of more songs to an external hard drive so that you can copy them onto another machine or simply listen to them from another computer. It is straightforward to do this using the iTunes interface.
Connect your external hard drive to your computer.
Open iTunes and scroll through your music library to locate the track you wish to copy.
Right-click on the track you wish to transfer and click "Copy" on the menu that appears.
Click the Windows "Start" button, and then click "Computer."
Locate you external hard drive on the folder tree on the left. Click on your drive.
Right-click anywhere in the panel on the right of the window, and then click "Paste."
You can transfer more than one tune at once by holding down the "CTRL" key and left clicking on all of the tracks you wish to copy, before right-clicking and selecting "COPY" in step 3.
If you copy music you have purchased from the iTunes Music Store, you will need to authorise it to play via iTunes on a different computer. You will need to provide your Apple account password to do so. If you do not authorise the computer, it will not be able to play the track(s).