PSP 3.90: Firmware/modding question.

I have: A phat PSP, a 1GB memory stick; and a completely un-modded 3.90 firmware.


I want: the easiest solution to downgrade it, so I can get the custom firmware required to download games (ISOs) via torrents or w/ever. In fact, lets just assume I want to play my own backed-up ISOs, so we dont upset any nerds who think I am pirating.


Ok, so... Solution?


Again, I dont care for any mods other than the downloading and playing of games, emulators for olds games etc.

Thanks, in advance.