How to downgrade my PSP without Pandora

I can’t play my games.. it says,”there are no games”.. and then i checked my memory stick, the games are still saved… I upgraded my PSP software to official 5.02. I need a custom firmware for 5.02 version… hoping that someone can probably solve this one as soon as possible. I have A fat psp Ver 5.02 is there any way i can downgrade so i can modify it to play games from the memory stick.. If anyone can let me know what i need to do so it would be of great help