You can customize Windows guest operating systems for the virtual machine when you deploy a new virtual machine from a template or clone an existing virtual machine. Customizing the guest helps prevent conflicts that can result if virtual machines with identical settings are deployed, such as duplicate computer names.

You can prevent Windows from assigning new virtual machines or templates with the same Security IDs (SIDs) as the original virtual machine. Duplicate SIDs do not cause problems when the computers are part of a domain and only domain user accounts are used. However, if the computers are part of a Workgroup or local user accounts are used, duplicate SIDs can compromise file access controls. For more information, see the documentation for your Microsoft Windows operating system.

Important: The default administrator password is not preserved for Windows Server 2008 after customization. During customization, the Windows Sysprep utility deletes and recreates the administrator account on Windows Server 2008. You must reset the administrator password when the virtual machine starts the first time after customization.



  1. Start the Clone Existing Virtual Machine or Deploy From Template wizard.
  2. Follow the prompts until you reach the Select clone options page.
  3. On the Select clone options page, select the Customize the operating system check box and click Next.
  4. On the Customize guest OS page, select an existing guest customization specification from the list and click Next.
    In the vSphere Web Client, you can also choose to create a new customization specification.
  5. On the User settings page, specify the required settings for the virtual machine.
    This page of the wizard appears only if the selected specification requires additional customization.
  6. On the Ready to complete page, review the details and click Finish.


When the new virtual machine starts for the first time, the guest operating system runs finalization scripts to complete the customization process. The virtual machine might restart several times during this process.

If the guest operating system pauses when the new virtual machine starts, it might be waiting for you to correct errors, such as an incorrect product key or an invalid user name. Open the virtual machine’s console to determine whether the system is waiting for information.

What to do next

After you deploy certain Windows operating systems that are not volume licensed, you might need to reactivate your operating system on the new virtual machine.

If the new virtual machine encounters customization errors while it is starting, the errors are logged to %WINDIR%\temp\vmware-imc. To view the error log file, click the Windows Start button and select Programs > Administrative Tools > Event Viewer.