Can't change hostname on captured W8 image

Hi, I've captured an image of Win 8 Enterprise where I allready have set up a test lab in Hyper V.

I used ImageX to capture the image.

When i deploy the WIM file using WDS with a unattended script i generated from the wim file using WSIM, it does not change the Host name.

The computers that I deploy this image to should only be be a member of the "Workgroup". Not a domain.

When i use <ComputerName>*</ComputerName> in the unattended file under settings pass="specialize", it just gives it the same name as the computer i captured the image of.
I tried adding the computer in AD with the GUID, and used <ComputerName>%MACHINENAME%</ComputerName> in the unattended file. But it didn't work.
Even if i use <ComputerName>TEST123</ComputerName>, it does not change the name.

Any suggestions?