1. A system comprising: a digital content library configured to store audio visual (AV) content, the digital content library containing one or more digital content files of AV content, each digital content file storing a list of valid identifiers; and a playback device coupled to the digital content library through a network, the playback device storing an identifier that identifies the playback device, the identifier comprising at least one of a temporary identifier and a renewable identifier, and the playback device further storing at least a portion of one or more digital content files downloaded from the digital content library for later playback, wherein the playback device is configured to: access and download, from the digital content library through a playback device interface, a group of different digital content files stored by the digital content library, only if the identifier stored in the playback device matches one of the valid identifiers in the list of valid identifiers for each of the different digital content files in the group, and play the downloaded AV content of the downloaded group of different digital content files, wherein the playback device is authorized to access and download the group of different digital content files for a predetermined period of time, wherein access by the playback device to the group of different digital content files is granted on a group basis, and wherein the playback device is prevented at the expiration of the predetermined period of time from accessing and downloading the group of different digital content files stored by the digital content library and prevented from playing the AV content of the downloaded group of different digital content files, and wherein preventing the playing of the AV content of the downloaded group of different digital content files comprises disabling the playback device.