Clasificación del S.O.

Windows 1.0.

Windows 2.0.

Windows 3.0.

Windows 3.1.

Windows 3.11.

Windows NT.

Windows 3.5.

Windows 3.51.

Windows 95. (Con 32 Bits).

Windows 4.0.

Windows 98.

Windows ME.

Windows 2000. (Profesional, Server, Advanced Server y Dataconter Server).

Windows XP. (Home, Professional, Media Center Edition, Table PC Edition, 64 Bit Edition y Starter Edition).

Windows 2003. (Home Server).

Windows Vista. (Home Basic, Home Premium, Business, Enterprise y Ultimate).

Windows Seven. (Starter, Home Basic, Home Premium, Professional, Enterprise y Ultimate).

http://www.masadelante.com/faqs/sistema-operativo 
http://www.baluart.net/articulo/las-6-versiones-de-windows-7 
http://www.publispain.com/trucos-xp/versiones_de_windows_xp.htm