The installer sets the MediaSourceDir property to 1 when the installation uses a source located on media, such as a CD-ROM. This property is not set when the installation uses a source located at a network location. For example, the SelectionTree Control uses MediaSourceDir to determine whether the installation is being run from source or run from a network location.
||Windows Installer 5.0 on Windows Server 2012, Windows 8, Windows Server 2008 R2 or Windows 7. Windows Installer 4.0 or Windows Installer 4.5 on Windows Server 2008 or Windows Vista. Windows Installer on Windows Server 2003 or Windows XP. See the Windows Installer Run-Time Requirements for information about the minimum Windows service pack that is required by a Windows Installer version.