Can I install a new machine with Windows 2008 and Exchange 2007 SP2 directly into the following existing environement:Windows 2003 SP2 DCsSLDone 64 bit Exchange 2007 RTM server on Windows 2003 R2 SP2 (Exchange not service packed at all because of the SLD problem)If not what is the recommendation? Carol

Yes, make sure that OS is 2008 and not 2008r2..Raj

Note the latest guidance:http://msexchangeteam.com/archive/2008/02/15/448140.aspxSingle-label Domain Names and Exchange Server 2007 SP1 (Part Deux)http://msexchangeteam.com/archive/2009/11/30/453327.aspxUpdates to the Exchange Supportability Matrix

Hi Carol, While the RTM version of Setup did not block installation into environments containing single-label domain names, it's not recommended. For recommendations, see the articles provided by Andy. Thanks, Elvis