Useful Official Updates Firmware download
Firmware 1.5
-the fully unlocked firmware
http://dl.qj.net/PSP-Firmware-1.50-File-(EBOOT)-North-America-Gaming-Consoles-PSP/pg/12/fid/163/catid/163
Firmware 2.0
-able to downgrade without eloader
http://dl.qj.net/PSP-Firmware-2.00-File-(EBOOT)-North-America-PSP/pg/12/fid/280/catid/163
Firmware 2.71
-able to downgrade without eloader
http://dl.qj.net/Firmware-2.71-PSP/pg/12/fid/8046/catid/163
Firmware 3.03
-able to downgrade with GTA + Xloader
http://dl.qj.net/PSP-Firmware-3.03-PSP/pg/12/fid/11844/catid/163
Firmware 3.50
-able to downgrade with Lumines + Xloader
http://dl.qj.net/PSP-Firmware-3.50-%28Japan%29-PSP/pg/12/fid/13829/catid/163
TO UPDATE, make a folder called UPDATE (PSP/GAME/UPDATE/)
and put the eboot file in there
