Oops I forgot to ask what type of applications are installed on the GOS, since running sysprep doesn't delete installed applications but it strip out the machine-specific settings like activation ID and SID of the system. Don't run sysprep if your running application such as MSSQL, Exchange or any application using activation ID.
'Enter System Out-of-Box experience option in sysprep? It keeps the installed apps right but will remove it form the domain?
Right it reset activation ID, SID and remove from domain.
Sysprep Process Overview http://technet.microsoft.com/en-us/library/hh825084.aspx
Thanks