Twenty-five years ago, on Nov. 20, 1985, Microsoft introduced its first version of Windows to the world. Not many people outside the technical press or the tech industry took notice. Product launch events that cost hundreds of millions of dollars were still years away.

What's changed in Windows in the last 25 years? Plenty. In this image gallery, we take a look at the various faces of Windows over the past couple of decades and clue you in to what happened at every stage of the operating system's development.

1985: Windows 1.0

Screenshot courtesy of Microsoft.

Windows started in 1981 as a project called Interface Manager and experienced a series of delays getting out of the gate. When it was finally released in late 1985 as Windows 1.0, it made a ripple, not a splash. It had to be run on top of DOS, few applications were written for it, and application windows couldn't be overlapped (they had to be tiled).

Still, the OS allowed for multitasking of Windows apps (not DOS ones) and, even though few knew it at the time, it would eventually become the foundation for the Microsoft empire.

Windows 1.0 shipped with a handful of apps, including the Notepad text editor, a rudimentary calendar and the long-lived graphics painting program Paint. The operating system required MS-DOS Version 2.0, 256KB of memory and a graphics adapter. It could be run either from a hard disk or on two floppy disks running simultaneously -- in other words, you couldn't swap the disks in and out of a single drive.