On an earlier post regarding the release of 6.38 OFW for the PSP, my advise was to not upgrade to 6.38 because it patches exploits used to run Hen and other fun things on your PSP. With some1’s 6.38 to 6.20 Downgrader, this warning is moot now but of course it still applies to 6.39 (until the release of the 6.39 downgrader that is)

If you somehow upgraded to anything above 6.35 OFW and need to downgrade, then read on. This guide will help you install 6.38 OFW on your PSP so you can downgrade to a much more usable firmware, 6.20 OFW.

Requirements:
Download 6.38 OFW for your PSP model

• PSP-2000
• PSP-3000
• PSP Go

How to upgrade your PSP to 6.38 OFW

• Extract the FW zip file on your PSP
• Copy the resulting EBOOT.pbp to x:\PSP\GAME\UPDATE (x is your memory stick or the PSP Go‘s storage)
• On your PSP, run the 6.38 updater.
• Follow on screen prompts

After upgrading to 6.38 OFW, you can proceed to downgrade using this guide: Downgrade 6.38 to 6.20 OFW PSP