Sharing my story, hope it's helpful for somebody.
I'm an iTunes subscriber and I have gigabites of m4p files on my machine. Of course I enjoyed them on iPod. But last month my iPod was stolen (sh*t!) and I've got a new zune player on my birthday! Obviously I couldn't copy my M4P collection to it because these file had iTunes DRM protection. Fornately I found http://mp4-converter.info and converted all my iTunes files just in few clicks!So I would recommend this if you have any problems with protected files - it will convert them to unprotected MP3 or any other format so you can play them without iTunes application. Tell me if you need exact will go thru my mail