There are a couple ways to determine your Windows AD Schema Version: ADSIedit.msc and/or LDP.exe. In this article I use ADSIedit.msc.
Note: The sample domain used in this article is Servusinc.com. Substitute this domain with your own AD domain.
13 -> Windows 2000 Server
30 -> Windows Server 2003 RTM, Windows 2003 With Service Pack 1, Windows 2003 With Service Pack 2
31 -> Windows Server 2003 R2
44 -> Windows Server 2008 RTM
47 -> Windows Server 2008 R2