You will have to have a Pandora battery and magic memory stick to do it, it is the only way, I do not care what you may have read somewhere but that is the only at that firmware.
hi hope you can help i have a psp slim 2003 date code 7c running version 4.00 can you tell me if it downgradeable or not and if not can i use the pandora method and if i can use the pandora method is it best to do the mem stick first or the battery first and is it essential to buy a spare battery or is it just a good idea hope you can help