In the Registry under HKLM\System\Setup!UnattendFile
In the %WINDIR%\Panther\Unattend folder but only when Setup is run from a previous version of Windows as opposed to using Windows PE.
In the %WINDIR%\Panther folder –This is where Setup caches answer files after the windowsPE and offlineServicing passes are finished.
On writable removable media such as a USB flash drive – This is checked in order of drive letter and the answer file must be at the root of the drive and be named either Unattend.xml or Autounattend.xml.
On read-only removable media – Again, this is checked in order of drive letter and the answer file must be at the root of the drive and be named either Unattend.xml or Autounattend.xml.
In the \Sources folder in a Windows distribution (during the windowsPE and offlineServicing passes) and in the %WINDIR%\System32\Sysprep folder (during all other passes)
In the %SYSTEMDRIVE% folder
For more information on deploying Vista, see my series of articles on WindowsNetworking.com starting with http://www.windowsnetworking.com/articles_tutorials/Deploying-Vista-Understanding-Windows-AIK.html.
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.