Application advertisement is a Windows Installer component that you use extensively when deploying applications through the Group Policy-based software installation feature. When you advertise an application, you don't actually install the application on the user's desktop; rather, you simply install the application's "presence." The presence can be a shortcut on the user's desktop or Start menu, a file association in the registry, or even a COM component registered in HKEY_CLASSES_ROOT. Advertising implies to the user that the application is installed and ready to use. However, the application files themselves aren't actually installed until the first time the user runs the application. The advantage to advertising is that it makes applications available but installs them only when needed. Thus, if you manage 20,000 desktops, advertising lets you worry about updating applications only on the computers that have actually used the applications. The downside of advertising is that a user who needs an application must wait several minutes for the system to install the application before he or she can use it for the first time.