From PSP Developer Wiki
The PSP has many file structures
- ms0:\ISO - Put your UMD Game rips here. They MUST be in .iso or .cso file format.
- ms0:\MUSIC - This is where you obviously place music files. File formats supported are .mp3 and .wav. *.wav playback must be activated.
- ms0:\PICTURE - This is where you place your images. File formats supported are .jpg/jpeg and .bmp. (I believe thats it.)
- ms0:\PSP - Contains folders that the PSP saves data in. Saves, cookies from the browser, etc.. More info on that later.
- ms0:\VIDEO - This is where you place you videos. The PSP only reads .mp4 files at some specific video resolutions. Some are 320x240 and 368x208.
- ms0:\seplugins - This folder will contain plugins for your PSP. Not required to have unless, of course, you have plugins. Some popular plugins are cxmb (Custom XMB) and CWCheat.
- ms0:\ISO\VIDEO - This is where UMD Movies/Videos go. They MUST be in .iso format.
- ms0:\MUSIC\*foldername* - This folder can be named anything. Its a one of the few "good" features to organize your music. If you like organizing by albums or artist or even type of music this could benefit to you. You can have as many folders in the MUSIC folder as you like. The PSP cannot shuffle music from 2 different folders.
- ms0:\PICTURE\*foldername* - Like the Music subfolders, this is similar. Just name the folder anything you like. Useful to, again, "organize" things in your PSP.
- ms0:\VIDEO\*foldername* - Same thing as the PICTURE subfolder. Used to "organize" things in your PSP.
- ms0:\PSP\GAMEXXX - This folder is related to the firmware on your PSP. If you are on 3.xx firmware then this folder will show up as "GAME3XX", 5.xx will show up as "GAME5XX", and so on. It is rarely used.
- ms0:\PSP\GAME150 - This folder is mainly used by Slim PSP owners who want to use homebrew "exclusive" to the PSP Phat. It may or may not work depending on the homebrew. *Homebrew will not be explained in this guide.
- ms0:\PSP\COMMON - This is usually where unknown/unsupported file formats downloaded from the PSP web browser are saved.
- ms0:\PSP\GAME - This folder is where all applications/homebrew, demos, and updates belong. They each have to have their own separate folder. Explained further down.
- ms0:\PSP\MUSIC - Same as the MUSIC folder located in the root of the Memory Stick.
- ms0:\PSP\PHOTO - Same as the PICTURE folder located in the root of the Memory Stick.
- ms0:\PSP\SAVEDATA - This is where all your game saves are stored. If they are deleted, then there goes your data. Replacing saves does no harm. Just make sure you back it up before you do.
- ms0:\PSP\SYSTEM - This folder contains data from features like Skype and RSS.
- ms0:\PSP\GAME/UPDATE - This is where your general firmware updates go.
- ms0:\PSP\MUSIC\*foldername* - Same as MUSIC/*foldername*.
- ms0:\PSP\PHOTO\*foldername* - Same as PICTURE/*foldername*.
- ms0:\PSP\SYSTEM\BROWSER - This is where the PSP stores browsing histroy, favorites, etc..
- ms0:\PSP\SYSTEM\RRSCH - This is where the PSP stores your RSS channels.
- ms0:\PSP\SYSTEM\RSSCH\CHANNELS - Your RSS channels.
- ms0:\PSP\THEME - This is where you put your .ptf themes. If you have the cxmb plugin, then this is where you put your .ctf themes.
- ms0:\PSP\LICENSE - This is where the PSP saves licenses from things you bought from the PSN store. You cannot, I repeat, YOU CANNOT use things you bought on one PSP on another. Not even if you copy the license folder to the other PSP. Flashing your firmware will also render your bought games from PSN un-playable as the system will recognize it as a new, different PSP.
- ms0:\PSP\GAME\RECOVERY - This is where a recovery folder goes in case your PSP ever bricks and you still have access to the Recovery Menu.