Windows Installer Components

A component is a piece of the application or product to be installed. Examples of components include single files, a group of related files, COM objects, registration, registry keys, shortcuts, resources, libraries grouped into a directory, or shared pieces of code such as MFC or DAO.

The installer service installs or removes a component as a single coherent piece. It tracks every component by the respective component ID GUID specified in the ComponentId column of the Component table.


Two components that share the same component ID are treated as multiple instances of the same component regardless of their actual content. Only a single instance of any component is installed on a user's computer. Several features or applications may therefore share some components.


Because components are commonly shared, the author of an installation package must follow strict rules when specifying the components of a feature or application. This is essential for the correct operation of the Windows Installer reference-counting mechanism. For more information, see Organizing Applications into Components.

In brief, these rules are:

  • Each component must be stored in a single folder.
  • No file, registry entry, shortcut, or other resources should ever be shipped as a member of more than one component. This applies across products, product versions, and companies.

For more information about using components, see