The paper describes DISCOVR, a distributed collaborative video recorder. DISCOVR is a P2P application that combines asynchronous file sharing with synchronous on-demand media streaming. DISCOVR uses a flat entity ID space, with the entity being any of the media file, header, mega packets, index and metadata. All DISCOVR entities may be asynchronously or synchronously distributed. DISCOVR adopts a sender-driven priority based sharing protocol. If the user is on-demand viewing a media file, those packets that are to be viewed in the near future will be put on the synchronous access list, which prompts its connected peers and the peers that are indirectly connected to fulfill the distribution of the on-demand packets in high priority. By letting the peers engage in both asynchronous sharing and synchronous on-demand streaming, DISCOVR promotes the peers to remain online longer, thus improve the availability of the P2P system and the overall performance.