The PlayStation Store offers games for download every month for free to subscribers of PlayStation Plus. However, if you happen to have custom firmware, which allows you to play disk images downloaded from the Internet on your system, many sites exist that allow you to download games for your PSP. These sites include Pirate Bay and IsoHunt. It is only legal to do so if you already own the game.
Please note that torrenting or downloading games you do not already own is illegal. Unless you acquire your game from the official site or from a reputable retailer, downloading these games is a breach of copyright law. Piracy will cost you more money than if you bought the game you wanted in the first place. This guide in no way encourages you to go out and steal the games from the developer, because copyright theft is still theft. Remember this if you decide to download or torrent games. This method is intended for backup purposes only, because a backup file is important to have in your possession when it comes to technology. Download the custom firmware and install it on your system. You can then begin downloading backup disk images.