A. Exchange 2010 is supported on the 64-bit edition of Windows Server 2008 with SP2 and Windows Server 2008 R2.

Exchange 2007 and Exchange 2007 SP1 aren't supported on Windows Server 2008 R2. Exchange 2007 SP2 isn't expected to add support for Server 2008 R2. Note that you can have domain controllers running 2008 R2, and they will work with Exchange 2007.

If you really want to run Exchange 2007 on Server 2008 R2, you could install Server 2008 R2 Hyper-V then run a Server 2008 virtual machine with Exchange 2007.

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