Hi all.

Maybe I can help with downgrading PSP from firmware 2.80 to 1.50. First of all, if you have a lower firmware version, you’ll have to upgrade to 2.80. Then download this file and put it in X:PSPGAMEUPDATE (with X: being your PSP). Then go to Game -> Memory Stickâ„¢ and open ‘PSPâ„¢ Update ver 2.80′.This method also uses the tiff exploit, which enables small pieces of code to be run through tiff files.
Please use Google or search on this forum to find these files: 1. HEN for Firmware 2.80 , 2. v2.80 Downgrader , 3. Firmware 1.50

Hope that will help to other members in future.