Regional Playback Control (RPC)
  Region Code 0 - region free

  Region code 1 - U.S. Canada, U.S. Territories

  Region code 2 - Japan, Europe, South Africa, Middle East

  Region code 3 - Southeast Asia and East Asia

  Region code 4 - Australia, New Zealand, Pacific Islands, Central America,
    Mexico, South America, Caribbean

  Region code 5 - Eastern Europe (east of Poland and the Balkens), Indian
    subcontinent, Africa, North Korea, and Mongolia

  Region code 6 - China and Tibet

  Region Code All - airplanes, cruise ships, etc. (may be same as 0)

Some dvd players give you 4 chances to select which permanent region 
  you want to configure it to.

Also, newer version of RPC on the disc will refuse to run on a 
  Region 0 or All player.