Hi
I just have to add a few words to Kendos post

1. Have a look at
THIS THREAD where many people offer free downgrading service.
2. I suspect that many Batteries you can buy are hardmodded so you cant do anything else with it. Also on some Slim PSP it is not possible to make / unmake pandora Batteries because it is physicaly disabled.

3. Hear the man, hear the man! for he speaketh the truth you mangy Pirate! ARRRRR!
4. Actualy i reccomend 2 Dumps ^^
Those Flash dumps are images of the PSP's Firmware and Registry and can be recovered with the pandora sets.
The first Dump before you install CFW is for the case that you need to send it to Sony while under guarantee.
The Second directly after installing CFW so you can jump there if you mess anything up on your PSP.
one before installing Customfirmware so you can