This document provides an overview of the history and key features of different Windows operating systems. It discusses the early versions of Windows from 1985 to 1990 and how Windows 3.0 introduced a graphical user interface. It then outlines the subsequent versions including Windows 7, which improved on Vista with better performance and a simpler interface. The document concludes by mentioning Windows 8 will likely be released in 2012 and provides references for additional information.