Adding first Windows Server 2008 R2 Domain Controller within Windows 2003 network

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Adddition Resources:
http://blogs.technet.com/b/askds/archive/2011/06/14/what-is-the-impact-of-upgrading-the-domain-or-forest-functional-level.aspx
http://technet.microsoft.com/en-us/library/dd378876(v=ws.10).aspx