If you have OFW 6.39 (Latest Version As Of June 12th 2011) you can upgrade straight to custom firmware. The hack ISNT permanent but there is a fast recovery tool to speed up the firmware boot.
How to install 6.39 Pro B6
1. Backup you're PSP incase.
2. Download the files at the bottom and paste the proupdate and fastrecovery folders in the root of the game folder.
3. Go to your psp and run proupdate.
4. When the writing comes press x to install the custom firmware.
5. Now remember it isnt permanent but you use the fast recovery tool to boot back into CFW faster.
Congratulations now you can run ISO's CSO's Unsigned PSX Games and Unsigned Homebrews. PM ME FOR ANY QUESTIONS!
VirusTotal - Free Online Virus, Malware and URL Scanner
MODELS THIS WILL WORK ON
1000 ~ YES
2000 ~ YES
3000 ~ YES (My PSP is a 3000)
PSP GO ~ UNKNOWN
IF YOUR PSP BECOMES BRICKED IT IS NOT MY FAULT HOWEVER THIS IS A VERY SAFE METHOD THAT WILL RARELY CAUSE DAMADGE TO A PSP.
CREDITS TO TEACHING ME THIS METHOD GO TO CORAJE187 OF PSP ISOS FOURM!
Please thank or add to my reputation if you found this guide helpfull. Happy Hacking MPGH!