Instructions
Downgrade your PSP with a downgrade program such as TimeMachine, then install your emulator by hooking up your PSP to the computer with the USB cable. Drag and drop the emulator to the appropriate folder in your PSP's database.
Download the ROM from a site that hosts them such as CoolRom and drag and drop it into the appropriate folder in your PSP's database. Run the emulator and open the ROM. Set the settings to the best performance and set the controls.
Change the background for another fun hack. Download the image you want, scale it on your computer to 480x272 and put it in the "Photos" folder in your PSP. Go to "Photos" on your PSP and select the picture and press "X." Next, select "Set as Wallpaper" and press "X" again.
Stream music from iTunes to your PSP with another great hack. Install MyTunesRSS on your computer and run the software. Continue through the setup and enter the data such as where your music is on your computer and press "Start Server."
Browse the Internet with your PSP, going to the site that MyTunesRSS sets up for you as a host. It will tell you this after setup. Play the music and turn up the volume. You can now listen to all of your music without worrying about how much space is on your PSP. Your only limit is the space on the hard drive of your computer.