How do you downgrade a PSP with v3.9

One is download some software and follow the guide to downgrade your psp. It often a difficult thing for many people. But you can go here for all the new updates and downloads on these hacks or mods www.pspcodes.eu This method is not really to hard just register at the site and download the files needed for your Pandora then downgrade "ANY" psp firmwire just register here www.pspcodes.eu
Another is physical method, The key to that daunting task, it seems, was to turn an ordinary PSP battery into a so-called "service mode trigger battery," resulting in something N00bz has appropriately dubbed "Pandora's Battery." To make one of your own, you'll of course need a spare battery, as well as a working homebrew-enabled PSP to set things up with.
The disadvantage is that you neea a spare battery and make it your own, i think it evne a hard thing for many people.