Go to the iTunes website and download iTunes to the computer.
Open iTunes on the computer and click on the tab for the iTunes store.
Open an iTunes account by clicking on the "Sign In" tab in the top right corner, then the "Create New Account" tab in the pop-up box.
Fill out the requested information.
Browse the iTunes store to find songs. Click the "Buy" tab listed next to the chosen song.
Approve the charge to a credit card, and download the song.
Go to Rhapsody's website and open an account. There is a monthly fee to access Rhapsody, but any song can be played at any time.
Search its music catalog to find songs.
Select the song and click "Buy." There is an additional fee to download a song in addition to the monthly membership fee.
Download the song to the computer.
Go to Amazon's website and create an account.
In the drop-down menu at the top left, select "MP3 downloads."
Type the song's name in the search box and click the "Go" button.
Click the "Buy MP3" button next to the song. Approve the purchase on a credit card.
Download the song to the computer, following the on-screen instructions.