Today I got this interesting error when deploying new VMs from a pre-defined template with customizations. Its basically failing on Setup is applying system settings part and to be precise on specialize pass of Microsoft-Windows-Shell-Setup of unattend.xml file.

Here is the screenshot:

At this point the only option is to press OK which will cause the VM to reboot, needless to say it will be constantly rebooting never taking you back to the actual login screen. Trick to get us out of this one is dating back to old XP days and SCCM troubleshooting during task sequence issues – press SHIFT – F10 ( Or F8) ! You should now have nice cmd window, navigate to C:\Windows\Panther\UnattendGC and look for file called setuperr.log, use notepad to open it up.

As you can see the god damn product key is not valid. Common issue when cloning customizations – you can end up cloning Server 2008 customizations and try to apply them onto Server 2008 R2 which will obviously fail. Only the product key seems to matter, everything else will be exactly the same between the two operating system from vCenter customizations perspective.

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Source: http://adriank.org/vmware-windows-could-not-parse-or-process-the-unattend-answer-file-for-pass-specialize/