VB Script and Wscript MSI doesn't use the WScript object; Create the script with plain CreateObject instead of WScript.CreateObject. Eg. if you have a script Dim wshShell Set wshShell = WScript.CreateObject("WScript.Shell") which works OK as a standalone .vbs file, but terminates the install when used as a custom action Replace it with Dim wshShell Set wshShell = CreateObject("WScript.Shell") Never / Do not use Vbscript as Custom Actions. Robust code is difficult write in script. Debugging script in the Windows Installer is difficult. Anti-virus products kill them. More Info Link 1; Link 2