Being able to play PSP games off of an external hard drive or computer used to be only a dream of Sony PSP owners. With the help of some independent developers, the PSP custom firmware scene has made this possible. This means you can back up all of your PSP games into ISO format and play them directly off of an external device like a computer or hard drive with USB adaptor.
Download the "SEPlugins" folder from the resource section of this guide. Inside your PSP's memory stick there is a folder called "SEPlugins." This folder will only be useful if your PSP is running custom firmware. If you are running custom firmware and the folder does not exist, create it by right-clicking inside of the memory stick, once you have connected it to your computer, and click "New" and "Folder." Rename the folder to "SEPlugins."
Connect your PSP to your computer with its USB cable and it will automatically go into USB mode. Copy the files found inside of the downloaded SEPlugins folder into your PSP's folder of the same name. Press the "O" button the PSP to disconnect your PSP from the computer, but keep the USB connected to it. Hold the power button up until the PSP boots off.
Hold the right trigger button on the PSP and turn it on. You will be brought to the recovery menu of the PSP. Press the arrow button on the PSP until you get to "Plugins." Enable both "CFE_loader.prx" files inside of the plugins section. Exit the recovery menu by selecting the "Exit" button on the main menu. Your PSP will reboot.
Your computer will ask you to install drivers for the PSP because you are now running it with the extender active. Click "Yes." Locate where your PSP games are on the computer. Hold the "Music" button on your PSP and press the right trigger button to bring the CFE menu up. Press the right arrow button on your PSP and you will be able to browse your computer's files. Select your game to begin playing.
Creating backups of your own games is legal, but distribution of them is illegal.
Do not pirate your PSP games.