DOS is great! Read about its origins!
OS/2 is great! Read about its origins.
Windows 1.x History
Windows 2.x History and Origins
History of Windows 3.1 and variants
Windows 98, and ME – the operating systems of the late 90s and early 200s.
Windows NT 3.1 - Microsoft’s first foray into non-DOS kernels.
Windows NT 5 - moving into the future
Clippy’s best friend and grandfather – Microsoft Bob