The Microsoft® Windows® Installer is an application installation and configuration service. WindowsInstaller-KB884016-x86.exe is the redistributable package for installing or upgrading Windows Installer.
Note: for users of previous versions of the Windows Installer: The new Windows Installer redistributable, WindowsInstaller-KB884016-x86.exe, follows a new naming convention that contains a knowledge base reference so it is easier to identify which version of the Windows Installer will be installed. The previous naming convention, INSTMSI.EXE, will no longer be used.