http://wab.com/tools/Wab_Version_Changer_V2.rar
tu copie les dossiers "WabVersionChangerV2" et "WabVersionChangerV2%" dans \PSP\GAME
START : Quit without change
Square : Trick to Firm v1.0
Circle : Back to Firm v1.5
Triangle : Trick to Firmware v2.0
When is done you can go to System Settings =>
System Information and Check Your System Version :=)
Then launch the game!
Enjoy!!