Windows 8 and Windows Server 2012 Sysprep.exe supports a new command line switch called /mode:vm.
This switch is useful if you are installing Windows 8 or Windows Server 2012 in virtual environment like Hyper-V and you are going to deploy the image back to the same virtualization environment. For example let’s say you have a Hyper-V server and you want to be able to deploy new VM’S quickly. Here are the steps you would go through
Install Windows 8
Configure it the way you want
c:\windows\system32\sysprep\unattend.xml to automate OOBE
%windir%\system32\sysprep\sysprep.exe /oobe /generalize /shutdown /mode:vm
Back up the .VHD for the VM to location
Create a new VM and attach copy of the .VHD
Note: This switch is only supported for virtual machines. You can’t mix and match Hyper-V VMs and VMWare VMs. Also, you cannot deploy this image to physical machine.
Additional Information: http://technet.microsoft.com/en-us/library/hh825033.aspx