Downgrade your PSP 5.50 or any other firmware with a Pandora battery. There are or should be more ways to downgrade, but using a Pandora battery is much safer and very easy. Not only can you downgrade but also install Custom Firmware (CFW) making your PSP be able to play full games entirely from the memory stick. Latest CFW at the moment is 5.50 Gen C. Note you will also need a magic memory stick. You can also buy it or just create your own. If you want to create your own easy follow this simple tutorial here!