Windows Installer interprets an installation package and installs programs on your computer. Installation packages include all data required to install/uninstall/configure an application. (including .msi file that contains an install database, summary information, additional component tracking, and references to internal/external required files. Files associated with Windows Installer may have these extensions: msi, msn, msp, mst, idt, cub, pcp. msiexec is also a command line entry to install products.