In Windows 7 the built in local administrator account is disabled by default.
To automatically enable the local Administrator account you will need to add the following component to your Autounattend.xml or the system unattend.xml file.
<component name="Microsoft-Windows-Deployment" processorArchitecture="x86" publicKeyToken="31bf3856ad364e35" language="neutral" versionScope="nonSxS" xmlns:wcm="http://schemas.microsoft.com/WMIConfig/2002/State" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> <RunSynchronous> <RunSynchronousCommand wcm:action="add"> <Path>net user administrator /active:yes</Path> <Order>1</Order> </RunSynchronousCommand> </RunSynchronous> </component>