DRM(Digital Rights Management): It is a kind of controversial technology which provide access control for digital media. As we all know, the M4V movies you purchased or rental from iTunes are DRM protected and limited to play on Apple devices only. You are not allowed to post the purchased movies to others, upload to website or play the movies on other devices you own for personal use even if you are the owner of the movies. All the limitations are caused by Apple DRM protection policy. And this really makes us feel unfair sometimes. So we have to remove DRM protections in order to play the movies on other players freely, such as Nokia N97.