Setup Factory for Windows Installer
Creates a custom action that sets the value of a property. Corresponds to Windows Installer custom action type 51.
See the Attributes tab for more details about scheduling, run options and return values.
The ID of the property that you want to set the value of. You can right-click on the field and choose Insert > Property to see a list of common or already defined properties, or click the Browse button to open the Insert Property dialog.
The value of the property. You can use an absolute value like "My new value" or use properties as part of the value such as "[OTHERVALUE]."
MSDN Online: CustomAction Table
MSDN Online: Custom Action Type 51
MSDN Online: Summary List of All Custom Action Types
WiX Help File: CustomAction Element