The trick is when you want to use different unattend.xml files for different target machines. To do this, you need to use the wdsutil.exe utility to pre-stage them. For more information on how to do this, type wdsutil /add-device /? at a command prompt.
Mitch Tulloch was lead author for the Windows Vista Resource Kit from Microsoft Press, which is the book for IT pros who want to deploy, maintain and support Windows Vista in mid- and large-sized network environments. Mitch was also the author of Introducing Windows Server 2008 and technical project lead for the Microsoft Office Communications Server 2007 Resource Kit, both books also from Microsoft Press. For more information on these and other books by Mitch, see www.mtit.com.