MBR is the file extension that is specific to the Zune media player. It is also a service for purchasing such files on the web. An MBR is a file used to store the location information of digital audio or video content. Using this information, the Zune can play content that the MBR file points to in a streaming fashion. There is no need to store multimedia data locally on the computer hard drive.

Zune is a Microsoft product.