Get another battery. You should of had backup files on your PSP battery.
Custom firmware is needed to do it, and if custom firmware is installed on the PSP in use, a plugin can be installed.
Get a pandoras battery and magic memory card...
Recently you can not make your psp with a custom firmware with out Pandora, Think about buying a Pandora battery on eBay, they are cheap.
It is impossible without the use of a Pandora Battery or Magic Memory stick.
Right now there isn't. If you want to get custom firmware for psp version 6.20 you need to downgrade to custom firmware using a Pandora battery.
Make or buy a pandoras battery
You're in luck! There seems to be a homebrew enabler out for official firmware 5.03. http://www.youtube.com/watch?v=lPMiNTbL7YQ
No, you can't. And even with a Pandora Battery, you cannot downgrade the 3000 or the late 2000 model.
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Cause you need to make you PSP Go To the lowest firmware (kinda like downgrade) Then you can install you custom firmware
New version comes out is the best version but i should be custom firmware because without custom firmware you can not play free games in PSP.
Hacking the firmware depends on the PSP's motherboard, not the current firmware installed. If you're asking whether or not it can be made into a custom firmware, then the answer is yes, but all homebrew would have to be rewritten for it.