This is the body of a paper (without an intro and conclusion) detailing the progression of the Windows 3.1 operating system to Windows 95 to NT 4.0. Windows 3.1 is first discussed, along with a description of its advantages over both the previous operating system, DOS (Disk Operating System) as well as previous versions of Windows. The limitations of the OS are also discussed to explain the natural progression to Windows 95, a far more powerful OS. The development of Windows NT 4.0, a major milestone in the evolution of the operating system in corporate and network environments, is discussed along with its necessity in the market. 7 pgs. 8 f/c. 5b.