Did you realize that Windows will be 25 years old this year? The "Premier Edition" of Windows 1.0 was released to vendors and partners in summer 1985. That fall saw the release of the first retail edition: Windows 1.01.
In The Secret Origin of Windows, Tandy Trower writes about his time at Microsoft, including working to bring Windows from (essentially) vaporware to a product in about a year. It's an interesting read.
While this was a monumental effort, and my hat is off to the guy for pulling it off, I sometimes wonder how many programming hacks and bugs from Windows 1.01 still persist in Windows 7?