[This is preliminary documentation and subject to change.]
The figure above illustrates the interaction between the operating system, the installer service, and an uninstalled advertised product during a product level installation. Because an uninstalled product cannot call the installer itself, the installation of the product requires that the operating system employ the installer's API. It is therefore possible to advertise an entire product when using the installer with Windows NT 5.0 because both OLE and the Shell make use of the installer's API. As illustrated in the figure, when a user activates the advertised product from an entry point the operating system calls the installer to install the product. After the installation is completed the installer returns a path to the now installed product back to the operating system which then launches the application.
Product level installation is a central part of the installer's capability of supporting system management by using assigning and publishing.