Methods and apparatuses whereby legally obtained media files are marked so they are associated with the legal owner. A legally obtained media file is delivered normally, without any form of interruption. However, when an illegally obtained media file is delivered, a message file is delivered in association with the media file.According to an embodiment, a method of the invention comprises receiving a media file, retrieving an identifier that uniquely identifies a player unit, appending the identifier onto the media file, and storing the appended media file in a data storage medium.According to another embodiment, a method of the invention comprises receiving a media file with a first identifier, retrieving a second identifier, comparing the first identifier with the second identifier, retrieving a message file from a non-volatile memory and producing a message output if the first identifier does not correspond to the second identifier, and producing a media output from the media file.