A nice post about Windows Server 2008 and Exchange Server 2007 SP1.
In a previous blog post, we wrote about the various versions of Exchange Server and their support for Windows Server 2008. Now that Windows Server 2008 has released to manufacturing, we wanted to briefly discuss some specific issues that you might encounter as you deploy Windows Server 2008 in your environment, particularly if you're planning on running Exchange Server 2007 Service Pack 1 (SP1) on Windows Server 2008.
Exchange 2007 SP1 is the only version of Exchange Server that is supported for installation on Windows Server 2008. Now that Windows Server 2008 has RTM'd, Exchange 2007 SP1 is fully supported on Windows Server 2008 in production environments. No other version of Exchange Server, including the released to manufacturing version of Exchange 2007, is supported on Windows Server 2008.
As stated in the blog, Mission Impossible: In-Place Upgrading Microsoft Exchange Server 2007 from Windows Server 2003 to Windows Server 2008, you cannot upgrade the operating system in-place while Exchange 2007 (RTM or SP1) is installed. Thus, the only way to run Exchange 2007 on Windows 2008 is to do a fresh install of Windows 2008 and then install Exchange 2007 SP1.
Read more at source: http://msexchangeteam.com/archive/2008/03/05/448338.aspx