To customize a Windows guest operating system, the virtual machine must meet certain requirements.

The following are the requirements for Windows:

The guest operating system is not a primary or backup domain controller.

The clone or template has the Windows versions that is supported for Guest Customization. For a list of Windows operating systems supported for guest customization, see the vSphere Compatibility Matrixes at http://www.vmware.com/pdf/vsphere4/r40/vsp_compatibility_matrix.pdf on the VMware vSphere documentation Web site.

Windows XP Home or Windows NT4 operating system guest customization is not supported.

The guest operating system has the most recent version of VMware Tools installed.

The Microsoft Sysprep tools are installed on the vCenter Server system.

Microsoft Sysprep tools have certain requirements and impose certain restrictions on the source machine.

If the virtual machine resides on a host running ESX Server 3.0.x or earlier, both the active partition (the partition containing boot.ini) and the system partition (the partition containing the system directory, for example, \WINNT or \WINDOWS), must be on the same virtual disk.