How to downgrade PSP Slim?

How to downgrade PSP Slim?(Urgent)?

• I have got the magic memory stick and I know how to create the Pandora Battery with PSP Slim Battery.Now, what should I do to downgrade PSP Slim (3.90 OFW) with these two things?

• Answer:

  The magic memory stick does the downgrading for you, it will flash the firmware with whatever version the magic memory stick holds. What you do is: 1) insert the magic memory stick, 2) power off the system and Remove the standard battery, 3) carefully insert Pandora's battery and the system will boot Automatically, so be careful that the power doesn't get cut at any time until the process is complete, 4) simply follow the onscreen instructions until the firmware is flashed, after the system powers off (automatically, if I remember correctly) then 5) remove pandora's battery and insert the standard battery, then power on and Voila! You should be running custom firmware. Check the System Info tab to check the version, I think.