November 10, 1983, the day on which Bill Gates first unveiled Windows 1.0 to the world. He did so during an unprecedented elaborate event at the Helmsley Palace Hotel in New York City. An extension to the popular MS-DOS, Windows 1.0 has a graphical user interface, with menus, icons, tiled windows, and multitasking.
Bill Gates predicted it would run on 90% of the world's PCs by the end of 1984. The reality was a tad bit different - Windows 1.0 didn't see release until 1985, and probably sold around 3 copies. However, as is often the case with Microsoft, the company persisted, and years later, it would be the dominant force in the operating system industry - and it still is today.