The Microsoft Windows Installer is an application installation and configuration service. Instmsi.exe is the redistributable package for installing or upgrading Windows Installer. Windows Installer is a component of the Windows 2000 operating system and that simplifies the application installation process. Windows Installer manages the installation and removal of applications by applying a set of centrally defined setup rules during the installation process.
These setup rules define the installation and configuration of the installed application. In addition, you use this service to modify, repair, or remove an existing application. The Windows Installer technology consists of the Windows Installer service for the Windows operating systems and the package (.msi) file format used to hold information regarding the application setup and installations. This version is the first release on CNET Download.com.