To determine whether a computer system has previously been sysprepped, look under the following registry key:
HKEY_LOCAL_MACHINE\System\Setup key
If you find a value named CloneTag under this key, the system has been sysprepped (i.e. generalized) and the value of this key will tell you when this was done.
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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.