Windows Installer Concepts and terminology. Windows Installer is an engine you can use to manage the state of an application. The state of an application includes installation, modification, upgrade, or removal. Windows Installer is not a software distribution technology. Software-distribution technologies use Windows Installer to install and manage software applications. Currently, most software distribution technologies rely on Windows Installer's command-line capabilities to install and manage Windows Installer–based applications. The Windows Installer service uses information in a Windows Installer package file to manage all phases of installing a program-- add, change, upgrade, and remove. The Windows Installer service performs all installation-related tasks as needed by copying files onto the hard disk, making registry modifications, creating shortcuts on the desktop, and displaying dialog boxes to capture user installation preferences. Windows Installer enables you to customize a broad set of applications in standard ways by using the following: · Command-line options. · Properties (variables) on the command line. Properties are variables that Windows Installer uses during an installation. A subset of these, called public properties, can be set on the command line. · Transforms. A transform is a collection of changes you can apply to a base .msi file. You can customize applications by using Windows Installer transform (.mst) files. You configure transforms to modify a Windows Installer package to dynamically affect installation behavior according to your requirements. You associate transforms with a Windows Installer package (an .msi file) at deployment time. Windows Installer Client The Windows Installer client is any application that calls Windows Installer to perform a task. Some common clients include the following: · The Windows-based shell. · Add or Remove Programs in Control Panel of Windows XP Professional and Windows 2000 Professional. · Windows Installer-enabled applications, such as Office 2000. · Software distribution technologies, such as Systems Management Server (SMS) and the software installation component of Group Policy included with Windows .NET Server and Windows 2000 Server. The Windows Installer client is responsible for user interactions such as displaying the Setup user interface during an installation. For example, the Windows Installer client uses the Windows Installer service to change the computer state by copying files and writing registry changes. Earlier approaches required each application vendor to deliver a unique program for each installation state change for every application.