How to delete every instance of an iTune

If you delete a file from one of your iTunes playlists, it doesn't get deleted from your iTunes library.

That's not a good thing if you want to keep your disk from getting filled up.

But you can delete the file from the library too if you use the [ OPTION ] key:

Hold down option when deleting the file and it removes it from the library and gives the option to remove from your drive.

via [ Jonathan Greene of atmasphere.net ]