Recently in Japan (and even in America and Europe), Sony as been implementing Mod Chip Protection into their games so that you can only play them on the system for which they were intended. If you try to play them on a system with a Mod Chip, then the game will display a message and freeze. This action has upset a great many people, and thankfully for us players, some people have been able to crack protection via Gameshark / Pro Action Replay codes.
Please take into account that these codes may not work on your Gameshark or Pro Action Replay unless you have a proper bios installed. For instance, my Gameshark 2.1 uses these fine, while my PAR I got in Thailand doesn't do anything. Soon I hope to add bios upgrades to the utilities section.
All codes were either generated with ModPAR, or derived from GameCopyWorld.Com or Asian Game Shark Code Center.