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.


Verify that all requirements for customization are met. See Guest Operating System Customization Requirements.

To perform this procedure, start the Guest Customization wizard when you clone a virtual machine or deploy one from a template.


  1. On the Select clone options page of the Clone Existing Virtual Machine wizard, select Customize the operating system and click Next.
  2. Type the virtual machine owner’s name and organization and click Next.
  3. On the Computer name page, enter a computer name for the guest operating system and a domain name.
    The operating system uses the computer name to identify itself on the network. On Linux systems, it is called the host name.
    Option Action
    Use the virtual machine name Select to use the virtual machine name, The computer name that vCenter Server creates is identical to the name of the virtual machine on which the guest operating system is running. If the name exceeds 63 characters, it is truncated.
    Enter a name in the Clone/Deploy wizard Select to be prompted to enter a name during cloning or deployment.
    Enter a name
    1. Enter a name.

      The name can contain alphanumeric characters and a hyphen (-). It cannot contain a period (.), blank spaces, or special characters, and cannot contain digits only. Names are not case-sensitive.

    2. (Optional) To ensure that the name is unique, select the Append a numeric value check box.

      This action appends a hyphen followed by a numeric value to the virtual machine name. The name is truncated if it exceeds 63 characters when combined with the numeric value.

    Generate a name using the custom application configured with vCenter Server Optional: Enter a parameter that can be passed to the custom application.
  4. Provide licensing information for the Windows operating system and click Next.
    Option Action
    For non-server operating systems Type the Windows product key for the new guest operating system.
    For server operating systems
    1. Type the Windows product key for the new guest operating system.
    2. Select Include Server License Information.
    3. Select either Per seat or Per server.
    4. If you selected Per server, enter the maximum number of simultaneous connections for the server to accept.
  5. On the Set Administrator Password page, configure the administrator password for the virtual machine and click Next.
    1. Enter a password for the administrator account and confirm the password by typing it again.
      Note: You can change the administrator password only if the administrator password on the source Windows virtual machine is blank. If the source Windows virtual machine or template already has a password, the administrator password does not change.
    2. (Optional) Select the Automatically logon as Administrator check box to log users in to the guest operating system as Administrator, and select the number of times to log in automatically.
  6. On the Time zone page, select the time zone for the virtual machine and click Next.
  7. (Optional) On the Run Once page, specify commands to run the first time a user logs in to the guest operating system and click Next.
    See the Microsoft Sysprep documentation for information about RunOnce commands.
  8. On the Network page, select the type of network settings to apply to the guest operating system.
    Option Description
    Use standard network settings for the guest operating system, including enabling DHCP on all network interfaces

    vCenter Server configures all network interfaces from a DHCP server using default settings.

    Manually select custom settings You can specify the IP address and other network settings for each network interface in the virtual machine.
  9. To specify IPv4 related settings, select IPv4 and enter IP address and other network settings.
  10. Select IPv6 to configure the virtual machine to use IPv6 network.
    The virtual machine can retain the IP address allocated from the network and IPv6 addresses. Microsoft supports IPv6 for Windows Server 2003, Windows XP with Service Pack 1 (SP1) or later, and Windows CE .NET 4.1 or later. However, these operating systems have limited IPv6 support for built-in applications, system services, and are not recommended for IPv6 deployment.
    1. Select Prompt user for an address when the specification is used. Selecting this option prompts you to enter either IPv4 or IPv6 address.
    2. Select Use the following IPv6 addresses to choose an IPv6 address from the list.
      • Click the pencil icon to enter additional IPv6 addresses. You can specify the full address or shorten it by using zero compression and zero suppression. You must specify at least one IPv6 address. You can edit an existing address, but you must not duplicate existing IPv6 addresses.
      • Enter subnet mask prefix. The prefix length must be between 1 to 128 where the default value is 64. Gateway is enabled by default, except when you choose Do not use IPv6.
  11. Select DNS and specify DNS server address and click OK.
  12. Select WINS and specify primary and secondary WINS information.
  13. On the Set Workgroup or Domain page, select how the virtual machine participates in the network and click Next.
    Option Action
    Workgroup Enter a workgroup name. For example, MSHOME.
    Windows Server Domain
    1. Enter the domain name.
    2. To add a computer to the specified domain, enter the user name and password for a user account that has permission.
  14. Select Generate New Security ID (SID) and click Next.
    A Windows Security ID (SID) is used in some Windows operating systems to uniquely identify systems and users. If you do not select this option, the new virtual machine has the same SID as the virtual machine or template from which it was cloned or deployed.
  15. Save the customized options as an .xml file.
    1. Select Save this customization specification for later use.
    2. Specify the filename for the specification and click Next.
  16. Click Finish to save your changes.


You return to the Deploy Template or to the Clone Virtual Machine wizard. The customization is finished after you complete the Deploy Template or the Clone Virtual Machine wizard.

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 and customize versions of Windows XP or Windows 2003 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.