if your psp is BEYOND firmware 2.80 then no homebrew for you, no isos, no psx games, nothing, the firmware that we want is 2.71 or lower, then you have to go to a process to make your psp to 1.5 and then 3.03OE-B wich allows non oficial sony programs, AKA homebrews
http://www.youtube.com/watch?v=dqvcHhbN2Lk Castlevania circle of the moon on an old GBA emulator
http://www.youtube.com/watch?v=WRVmOxx_bKg Castlevania simphony of the night on the psx emulator