The video files of the lectures by Slavoj Zizek and Antonio Negri during the Theaterformen festival are available online. In order to download the footage you need to save the torrents for Negri (italian/german) and Zizek (english).
BIt-torrent is a peer-to-peer client software that is available fr free dowload here. The files are encoded with the first open source video codec Ogg Theora, which has been released a couple of weeks ago and which is supported by various players on all operating systems. Windows and Mac users may download the nightly built of VLC VideoLAN player here. Linux users can try the Helixplayer or Realplayer you can find here. The Theora-Codec (for Realplayer!) is here (you gotta replace the ones shipped by Realplayer). Have fun!