Slim 2000 5.55, please help

Okay, so...I used to run 3.71 m33-2, if that's any clue as to how long it's been since I've messed with this stuff. I have a Pandora battery if needed. My PSP somehow updated itself to the 5.55 version of the official firmware, possibly because a while ago it had access to a wifi network for the first time ever and did it automatically?

I discovered this when I went to fire up one of my PSX EBOOTs and got a "copyright protection is invalid". I just wanna get back to a point where I can play...

Slim 2000 5.55, please help