Exchange 2007 SP2 installation can fail during the prerequisite check stage. The installation can fail for both the upgrade or for new installation of Exchange 2007 SP2. In the Exchange Setup log you can see that setup is failing. This can happen in the following scenarios: -You’re installing or upgrading to Exchange 2007 SP2 in an Active Directory forest that has only Windows Server 2008 R2 Domain Controllers; Or You’re installing or upgrading the Exchange 2007 SP2 in an Active Directory forest that has windows server 2008 R2 Domain Controllers as well Windows Server 2003 domain controllers that’re not updated to at least Windows Server 2003 SP1. “Once Windows Server 2008 R2 is released, Exchange team’ll release a web update for the Exchange 2007 SP2 Setup prerequisite XML files, which’ll add Server 2008 R2 as a supported Active Directory Domain Controller. Until then, bring up a domain controller that either has Windows Server W2003 SP1+ or Windows Server 2008 installed in your labs where you’re testing Windows Server 2008 R2,” announced.