VBScript Custom Actions are Not Windows Script Host It's a common assumption that VBScript CAs can use WSH constructs based on the WScript object model. But you cannot use script code such as WScript.CreateObject or WScript.Quit or WScript.Echo. The WSH environment provides the WScript object model, just as VBScript in a Web page uses an IE object model. Windows Installer scripting supplies objects such as the Session object for interacting with the install. You don't need WScript.CreateObject anyway—VBScript has a CreateObject method that does the same thing.