DVD’s and DVD players are made region locked while they are sold to the region during manufacturing,ie., DVD video discs may be encoded with a region code restricting the area of the world in which they can be played.In case you buy a DVD in the US and try to play in another country, the DVD player may not play the disc complaining “WRONG DISC” or something similar.
VideoHelp, has a huge collection of hacks for different DVD players and instructions on how to hack your DVD player to make it region free, and enjoy your movies.You can also search for hacks based on your DVD player model.
The Image below shows the Region Lock number for different places, region all/0 discs are not restricted and can be played any where.
Image : Wikipedia
Hack your DVD Player to make it region lock free @ DVD Hacks