seeing that there are too many questions asking about downgrading, i've decided to clear things up. hopefully, this can get stickied. before you start downgrading, YOU ACCEPT ALL RESPONSIBILITY FOR WHAT HAPPENS. you cannot blame anyone but yourself, if a brick happens. guides wouldn't be up if they didn't work. THIS IS FOR ONLY DOWNGRADING, UNLESS YOU USE THE UNIVERSAL UNBRICKER V3. the universal unbricker gives you a choice of official 3.71 or custom firmware 3.71 m33-2. installing custom firmware is highly recommended, but it is your choice. no one is forcing you. FOR ORIGINAL, FAT PSP RUNNING FIRMWARE 3.50 AND LOWER you can downgrade 3.50 and lower with exploits. -firmware 1.51 to 2.80. you can use the tiff exploit. it does not require any games. -firmware 2.81 to 3.03. you will need an UNPATCHED version of grand theft auto: liberty city stories, and download the neccessary files for downgrading. -firmware 3.10 to 3.50. you will need a copy of lumines: puzzle fusion, and download the neccessary files for downgrading. (only japan has the patched lumines. DO NOT USE IF IT REQUIRES 3.51) you can find downgrading guides HERE. BEFORE YOU START, you will need to know what motherboard you have. the provided link has a picture that will tell you what motherboard you have. ORIGINAL, FAT PSP RUNNING FIRMWARE 3.51 AND HIGHER there are no exploits to downgrade 3.51 and higher, as of now. you will need to create pandora's battery and magic memory stick or universal unbricker memory stick. there are many ways to get pandora's battery. i will list all ways. THE EASY WAY: 1. use a fat psp with custom firmware and run the installers. (highly recommended) THE COSTLY WAY: 1. buy the datel tool battery. 2. send in your battery to a reputable person. 3. buy a readymade battery (not recommended because it might be a regular battery) THE HARD WAY: 1. use a sony battery (1800mAh or 2200mAh), open it up, and remove a pin (ONLY FOR PROFESSIONALS) PANDORA'S BATTERY IS HIGHLY RECOMMENDED TO BE USED ON SONY BATTERIES. to make the magic memory stick, there are a few ways, but all are easy. 1. use a custom firmware psp, download and run the installer. 2. download TOTALNewbi installer, and choose what magic memory stick you want. you can find the files listed below: original 1.50 magic memory stick: HERE universal unbricker v3: HERE TOTALNewbi installer: HERE remember to read the README that comes with the files. it contains valuable information. FOR ALL PSP SLIM there is no downgrader, exploit or installer to get custom firmware, as of now. YOU WILL NEED PANDORA'S BATTERY AND ONE OF THE FOLLOWING MEMORY STICKS: 1. modified magic memory stick (not recommended, 3.60 m33 recovery menu may result in a brick) 2. universal unbricker v3 memory stick refer to firmware 3.51 and higher section for instructions on how to get the battery and memory stick. the pandora's battery/1.50 magic memory stick is only for fat psp's. it will downgrade back to 1.50, regardless of the firmware. the pandora's battery/universal unbricker v3 memory stick works for ALL psp's (fat and slim). as stated before, it will either put official 3.71 or custom firmware 3.71 m33-2. you choose which one you want. disclaimer: i do not take any credit to the guides in the links i have posted. all credit goes to the original poster.