OK I FOUND OUT HOW TO DO THIS TO MY 2.5 PSP. IT RESETS MY SETTINGS, DELETES MY CONNETIONS AND OTHER THINGS.

OK FIRST YOU TURN OFF YOUR PSP COMPLETLY.
I TURN IT ON WITH A UMD GAME IN (SOCOM)
IT AUTOMATICALLY STARTS THE GAME AND THEN I JUST EJECT THE GAME AND I GET THIS SCREEN WHICH DOES THE THINGS LISTED AT TOP.
HOPE THIS COULD BE USED FOR DOWNGRADING V2.5