Download Audacity Sound Editor if you don't have it already. (See link in "Resources" section.)
Download the instrumental version of the same song, using iTunes, Rhapsody or Napster.
Open Audacity and click "File > Open." Browse through your folders to find the two songs (instrumental and original). Highlight both of them and then drag and drop them into the Audacity window.
Zoom in and make sure the instrumental and original tracks are aligned. If they're not exactly aligned, use the double-ended pointer tool to slide one of the tracks to the left or right, until you see the sound waves matching up exactly.
Zoom all the way out until you can see the entire song again. Click an empty area in the instrumental track menu to highlight the entirety of the track. Click "Effect > Invert" from the toolbar menu.
Play the track to see if the music has been properly removed. If you still hear loud music, then zoom back in to check and see if the sound waves have been properly lined up. If not, adjust them until you get it perfect. When you're finished, click "File > Export as WAV" and save it to your desktop. You can now burn the file to CD or play it on your computer anytime you want.
Download the instrumental version of the same song, using iTunes, Rhapsody or Napster.
Open Cool Edit Pro 2 and click "File > Open." Browse through your folders to find the two songs (instrumental and original). Highlight both of them and then drag and drop them into the Cool Edit Pro 2 window.
Double-click the instrumental track to highlight the entire song. Click "Effects > Invert."
Zoom in and make sure the instrumental and original tracks are aligned. If they're not exactly aligned, use the pointer tool to slide one of the tracks to the left or right, until you see the sound waves matching up exactly.
Press "Ctrl" and highlight both tracks. Right-click them and select "Mix Down File." This will combine your tracks, turning the two different tracks into a single stereo file. Click "File > Save As" and give the track a name. Choose the folder where you want your track to be stored and then click "OK."