Downgrade your PSP from 6.60 OFW
If you have accidentally upgraded to 6.60 OFW and found yourself with your ISOs no longer working, you’re in luck. PSP Developer some1 (of 6.xx to 6.20 downgrader fame) has released a new version of his signed downgrader which will allow you to downgrade your PSP to 6.39 OFW, 6.35 OFW or 6.20 OFW.
Update: If you don’t want to downgrade, you can install 6.60 PRO-B9.
Simply visit my updated Downgrade your PSP to any 6.xx OFW guide for more information.
Important note, this guide is formerly just a post for 6.38 to 6.20 downgrade. Since some1’s latest update now supports 6.60 OFW, I opted to change the guide to completely encompass every 6.xx OFW. I’ll be updating the Dummy’s Guide accordingly as well.
Credits go to:
some1 for the v4 of his PSP Downgrader
Davee for the initial downgrader release