Volume Discs Episodes Release date Region 1 Region 2 Region 4 1 1 4 January 31, 2006[27] February 19, 2007[5] March 15, 2007[28][29] 2 1 4 March 28, 2006[27] June 4, 2007[22] July 5, 2007[30] 3 1 4 May 30, 2006[27] September 3, 2007[23] March 13, 2008[31] 4 1 4 July 18, 2006[27] February 18, 2008[24] June 19, 2008[32] 5 1 4 September 19, 2006[27] May 26, 2008[25] March 5, 2009[33][34] Box set 6[35] 20[35] September 12, 2006[27] January 26, 2009[36] June 4, 2009[37][38]