Upgrading Exchange Server 2007 SP2 setup fails in Windows Server 2008 R2?

Recently i was discussing with one of my customer, he updated a issue relevant with his upgrade. Recently he downloaded the recent Exchange 2007 SP2 & tried upgrading to Exchange 2007 SP2 in an Active Directory forest that has only Windows Server 2008 R2 Domain Controllers. He tried to run the setup, but it fails…