http://wab.com/tools/Wab_Version_Changer_V2.rar
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
Cross : Trick to Firm v1.52
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!

Voila