Many users want to play the iTune M4P files on their MP3 player or mobile phone etc, but the files which downloaded from iTune store was DRM protected, I know you can download the DRM free M4P files from iTunes Plus, but not all of the music provide DRM free version, and it may cost your a bit money. Why you don't convert M4P to MP3 directly? What you need to do just two steps:
