ok, as you may or may not know, psp has a new version of firmware. 3.0 and 3.1, sony has officially released this firmware for compatibility with the PS3. you have to have this firmware and have a ps3 to run the ps1 emulator right?...WRONG! an anonymous coder from psp-hacks.com has released a full working ps1 emulator homebrew for version 1.5. you can find it here.
http://www.psp-hacks.com/its the first thing on the page.