The file extension PKG identifies PlayStation Store Downloaded Packages, ie downloadable software from the Playstation Store. This includes movies, games and demos for the Playstation 3 and PSP. In addition, game updates in this format are offered. PKG files are encrypted files, which can be installed exclusively on the Playstation.
For PSP users, there is the free PC program 'Media Go' (with access to the Playstation Store), with which you can buy games, etc. and save as a PKG file on the PC. These files can be transferred to the PSP via USB cable and then installed.
Most often resolving problems with opening PKG files is very simple. Just install an appropriate program that supports such files. All of the listed programs support PKG files, but may vary in offered function and purpose. Some programs may be capable only of viewing contents of PKG files or offer file conversion options, but may not be capable of editing such files.
It is possible that although a compatible program has been installed on user’s system, it is not used by the system to open it. This may happen because no default application was associated with this type of files. To associate PKG files with given application, select "Open with" from drop-down menu (accessed by right-clicking on the file). Then select from the list the program or application you want to be used to open this type of file. If the Apple Installer applications is not on the list, select "Browse" option in order to manually locate the directory where Apple Installer has been installed.
Sometimes problems with opening PKG files may not lie with the application itself, but can arise due to other causes, such as: