A Windows Installer patch (.msp file) is a self-contained package that has the updates to the application and describes which versions of the application can receive the patch. An application that has been established using the Microsoft Windows Installer can be advanced by reinstalling an updated installation package (.msi file), or by applying a Windows Installer patch (an .msp file) to the application. Patches handles at a minimum of two database transforms and can contain patch files that are saved in the cabinet file stream of the patch package. Servicing applications by distributing a Windows Installer patch, relatively than a complete installation package for the updated product can have advantages. A patch can handle an entire file or only the file bits necessary to update part of the file. This can enable the user to download an upgrade patch that is much smaller than the installation package for the entire product. An update using a patch can protect a user customization of the application thru the upgrade.