How to Use RAR Files on Your PSPby Chad Anderson
Many PSP extras and games come compressed in the RAR format. The RAR archive, though a proprietary format, is popular because of the high-performance compression of the packages. Many users still prefer the RAR format over the standard ZIP format included with Microsoft Windows today. To use the items included in a RAR archive on your PSP, you need to use a desktop computer to "unrar" the archive, then transfer the decompressed files back to your PSP.
Launch a file browser window on your desktop, then navigate to the location where your RAR archive is saved.
Double-click the archive to open the RAR file in an archival program supporting "unraring." If you do not have an application that can do this, there are both commercial and free options available on the Internet (see Resources).
Click the "Extract" button to "unrar" the files, then close the application once the extraction is complete. Some applications may use a different terminology such as "Decompress" or "Unzip" in their dialogs.
Plug your PSP into the computer using the USB cable that came with the handheld, then open the PSP's Memory Stick in another file browser window.
Copy the extracted files from your desktop computer to the PSP's memory stick. Disconnect the PSP from the computer once the data transfer is complete.