Windows 1.01 (1985)
Windows 1.01 was a add-on for the then-popular MS-DOS. It was very simple at the time and not as popular as it was today. It consisted of very few applications, but was revolutionary for it's time.
Windows 2.03 (1987)
With the second major update to the Windows OS was Windows 2.03. A few apps were updated and changed. But perhaps most notably was the addition of Microsoft Office. At this time it only consisted of Word and Excel, and Powerpoint was added later on.
Windows 2.1 (1988)
Windows 3.1 (1992)
Windows 3.1 was the update that made Windows, well, Windows. While Windows and Microsoft were popular beforehand, but after 3.1 it became a household name. The update added games, a much easier to use interface, and much, much, more.
Windows NT 3.1 (1993)
Windows NT 3.1 was like Windows 3.1, but more suitable for businesses, making it easier to make graphs, enter statistics, and more business activities.
Windows NT 3.1 programs.