High Quality Content by WIKIPEDIA articles! A merge module is a special kind of Windows Installer database that contains the components needed to install a discrete software bundle. A merge module cannot be installed alone, but must be merged into a standard Windows Installer installation during the creation of the installation. Typically, a merge module or a collection of merge modules related by dependencies, installs a software product or portion of a product at runtime. The purpose of merge modules is to let you add self-contained software modules to multiple installations.