.MSI File Extension
File TypeWindows Installer Package
What is an MSI file?
An MSI file is a package that contains installation information for a particular installer, such as files to be installed and installation locations. It may be used for Windows updates as well as third-party software installers.
The contents of an MSI package may be extracted using a file decompression utility like 7-Zip.
NOTE: In Windows Vista, .MSU files are used to install system updates and hotfixes.