Important Files

C:\Windows/system32\eula.txt
C:\Windows\System32\license.rtf
C:\Windows\WindowsUpdate.log
# stores users' passwords in a hashed format (in LM hash and NTLM hash).
C:\Windows\repair\sam
C:\Windows\System32\config\RegBack\SAM
C:\Windows\repair\system
C:\Windows\repair\software
C:\Windows\repair\security
C:\Windows\debug\NetSetup.log (AD domain name, DC name, internal IP, DA account)
C:\Windows\iis6.log (5,6 or 7)
C:\Windows\system32\logfiles\httperr\httperr1.log
C:\Windows\\boot.ini	
C:\Windows\win.ini	
C:\sysprep.inf
C:\sysprep\sysprep.inf
C:\sysprep\sysprep.xml
C:\Windows\Panther\Unattended.xml
C:\inetpub\wwwroot\Web.config
C:\Windows\system32\config\AppEvent.Evt (Application log)
C:\Windows\system32\config\SecEvent.Evt (Security log)
C:\Windows\system32\config\default.sav
C:\Windows\system32\config\security.sav
C:\Windows\system32\config\software.sav
C:\Windows\system32\config\system.sav
C:\Windows\system32\inetsrv\config\applicationHost.config
C:\Windows\system32\inetsrv\config\schema\ASPNET_schema.xml
C:\Windows\System32\drivers\etc\hosts (dns entries)
C:\Windows\System32\drivers\etc\networks (network settings)
C:\Windows\system32\config\SAM (only really useful if you have access to the files while the machine is off)