Brewology

im guessing you on 3.52 M33 and to get to that menu u have to hard boot your psp (turn it all the way off for bout 5 seconds) then turn it on while holding R and you should get to the settings. go to configurations and changes the umd mode to M33 driver -NO UMD-

just to make sure check what firmware do u have.

or mybey the iso or cso is bad

He said his friend already got it to work once so it can't be the iso. Like newpspdude said, and if that doesn't work just stick any umd in the drive and then try and run the iso.