Something to have handy.
Freely copy iTunes Music Store files. PlayFair is an open source app that strips Apple’s DRM out of iTunes Music Store singles, allowing you to freely copy the music you pay for.
It takes one of the iTMS Protected AAC Audio Files, decodes it using a key obtained from your iPod or Microsoft Windows system and then writes the new, decoded version to disk as a regular AAC Audio File. It then optionally copies the metadata tags that describe the song, including the cover art, to the new file.