Link to information about MSI script-based custom action error codes 2738 and 2739

Heath Stewart posted an item on his blog this past week that I wanted to raise awareness about.  In the post, located at, Heath described some potential issues and workarounds for script-based custom action failures in MSI-based setups.

These error codes appear in an MSI log file when a script-based custom action fails to run correctly, and the error messages look like the following:

  • 2738, Could not access VBScript run time for custom action [2].
  • 2739, Could not access JScript run time for custom action [2].

A common resolution for this type of error is to re-register the file %windir%\system32\vbscript.dll and/or %windir%\system32\jscript.dll.  However, on Windows Vista this can present problems because if you attempt to re-register these DLLs from a normal user cmd prompt, the registration will be written to HKEY_CURRENT_USER instead of HKEY_CURRENT_MACHINE.

A key point Heath makes in his blog post that I was not aware of before reading it is that Windows Installer will not load and use scripting engines if they are registered in HKEY_CURRENT_USER (for security reasons that he described in more detail in his post).  Therefore, if you have registered the DLLs on Windows Vista from a normal user cmd prompt, that will not help fix this type of error.

If you have these scripting engines registered under HKEY_CURRENT_USER, you need to make sure that you remove that registration and re-register them under HKEY_LOCAL_MACHINE.  You can use the following steps to unregister them from HKEY_CURRENT_USER:

  1. Click on the Start menu, choose Run, type cmd and click OK
  2. To unregister the VBScript engine, run this command:  reg delete "HKCU\SOFTWARE\Classes\CLSID\{B54F3741-5B07-11CF-A4B0-00AA004A55E8}" /f
  3. To unregister the VBScript engine on a 64-bit OS, run this command:  reg delete "HKCU\SOFTWARE\Classes\Wow6432Node\CLSID\{B54F3741-5B07-11CF-A4B0-00AA004A55E8}" /f
  4. To unregister the JScript engine, run this command: reg delete "HKCU\SOFTWARE\Classes\CLSID\{F414C260-6AC0-11CF-B6D1-00AA00BBBB58}" /f
  5. To unregister the JScript engine on a 64-bit OS, run this command: reg delete "HKCU\SOFTWARE\Classes\Wow6432Node\CLSID\{F414C260-6AC0-11CF-B6D1-00AA00BBBB58}" /f

One last note - if you are a setup developer reading this post, I encourage you to read this post by Rob Mensching where he explains reasons why using script-based custom actions in an MSI can lead to bad results and should be avoided if at all possible.

<update date="7/29/2009"> Added steps to unregister the VBScript and JScript engines on 64-bit OS's. </update>