411 REFERENCE · Wikibooks
PSP/Downgrade to OFW 6.20
Reference material by Wikibooks contributors. This retains its source identity and is not 411 news reporting.
Download OFW 6.20 (use this file if you have a PSP Go)
Using your PC, create a folder named "PSP" on your PSP. Within the "PSP" folder, create a folder named "GAME". Within the "GAME" folder, create a folder named "UPDATE". (Folder names must be in all uppercase letters). The result will be ms0:\PSP\GAME\UPDATE.
Copy the EBOOT.PBP you downloaded to your UPDATE folder.
Download the 6.xx Downgrader, and extract it.
Copy the resulting "Downgrader" folder into the PSP/GAME folder.
From the XMB (home menu), under Game -> Memory Stick (or System Storage on PSP Go) select the Downgrader program.
In the downgrader app, press X to start the downgrade or R to exit.
After the Sony updater is finished you will get a message saying that "Settings Information is Corrupted". Just press the O button.
You have now downgraded to OFW 6.20.