My son bought a used PSP version 1.5. Since the previous owner left some junks into the BIOS/Firmware, he tried to clean it up and probably by accident remove too much stuffs. Now the PSP won't come up, when he power it up, the power light (green) come up, but nothing on the screen, after approximately 20 seconds, the PSP shut down by it sefl.

What is the solution. How can I restore the original firmware, etc...

If some experts is out there, please advice/help.