Files with the extension PBP, like a firmware update or a custom-made file, are used by the handheld Sony PlayStation Portable (PSP) gaming system to launch software. CSO is a file extension for up to nine levels of compressed ISO disk image formats. CSO files are used to archive PSP games. In order to compress PBP files into a CSO, a program like Microsoft Windows PSP ISO Compressor must be used.
Download the PSP ISO Compressor v1.4 for Windows from PSP-Hacks.com. It is available as freeware and can also compress in JSO and DAX formats.
CiSo Plus manufactures a free PSP ISO Compressor that reduces the resulting CSO file with a special feature called "Lost Areas." It also has dual-core enhancement and intelligent compression modes to enhance speed in gameplay.
The QPSP Manager 2.0 program by Softpedia works for both Microsoft Windows and Macintosh's Linux and OS X platforms. In additions to a PSP ISO compressor, it features a PSX ISO converter, application management, and a save-game backup system.
Make sure the program that you select for download does not have viruses, is from a trustworthy website and it is in the version (Mac or Windows) that you need.