When creating a virtual machine from a template in VMware Vsphere, most of you will make use of the “Guest Customization Wizard” to create a new SID for Windows Virtual Machines and other sort of things in which you want your new virtual machine to differ from the template.

Normally this is no problem, but when you want the newest of the newest like Microsoft Windows Server 2008 R2 64-bit, VMware doesn’t support guest customization, not even when you have updated your ESX and Virtual Center to the latest software-level. You get the following message:

“Customization of the guest operating system ‘windows7Server64Guest’ is not supported in this configuration. Microsoft Vista (TM) and Linux guest with Logical Volume Manager are supported only for recent ESX host and VMware Tools versions. Refer to vCenter documentation for supported configurations”

This error-message is known by VMware and they advise to install VMware Tools (http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1020716).
Off course the latest VMware Tools where already installed in the template and still the message occurred.

There is no actual solution for this problem, but there is a work-a-round;
Convert your template back to a virtual machine and go in to the properties of the virtual machine. Now on the Options-tab under “General Options” you see “Guest Operation System” where you can set the OS of the virtual machine. Change this from “Microsoft Windows Server 2008 R2 (64-bit)(experimental)” to “Microsoft Windows Server 2008 (64-bit)” and convert the virtual machine back to a template.

Now you will get the option of guest customization back when deploying a virtual machine from a Microsoft Windows Server 2008 R2 64-bit template.