Windows ultimate "popularity" (I use that word more to describe its marketshare, rather than actual affection for it among users..) has more to do with
network effects than anything else.
In simplest terms, once the sheer number of personal computers running Windows reached a critical point, the relationship between the number of programs that were available for it and the potential
market for developers of those programs resulted in a virtuous-circle. Virtually every program written could run on Windows because Windows was on 90%+ of the computers out there. Programmers who wanted to develop for competing platforms (ie. Macintosh, Amiga, Atari) were faced with the reality that they were serving but a tiny fraction of the market - so they didn't write for them. And because there weren't many programs for those platforms, they were never going to be as "popular" as Windows.
As I alluded to earlier, its important to keep in mind the size of the overall market for computers and software. In 1977 less than 50,000 "personal computers" were sold. By 1984 (the year the Mac came out, and Windows 1.0 appeared) the market had grown to about 6 million. A huge growth rate in percentage terms - but still tiny. The leading personal computer then, the Commodore 64, sold about 3 million units, the IBM PC about 2 million.
The difference, of course, is that because people writing software for
businesses were writing for the IBM PC, they could charge a lot more for their product than could people writing for Commodore 64s or the Macintosh. Businesses were
used to paying several hundred dollars for a spreadsheet, word processing, or accounting package. Consumers, however, weren't so thrilled about paying $80 or $100 for game or paint program for the Commodore.
The Macintosh was able to survive, if not actually thrive, during this period because its (then revolutionary) graphical user interface was well suited to specialized niche applications such as graphic design and page layout. Software packages such as Aldus (later Abode) Pagemaker took advantage of the high-resolution Postscript typefaces on the Mac and Laserwriter printer, and gave printshops and designers true "What You See is What You Get" control over the way documents printed. Aldus could sell Pagemaker for a high enough retail price that the Mac's relatively tiny marketshare didn't matter so much.
The first versions of Windows were market and technical failures. It wasn't until 1992, with the introduction of Windows 3.1, that it was a product "good enough" that most people buying computers would use it. The period from 1992 to 2000 saw PC-compatible sales skyrocket: from about 17 million annually, to 137 million. When Windows 3.1 first came out, Microsoft actually saw IBM's PS/2 as a greater competitor than the Mac. IBM had little success selling PS/2 to clone makers, so they ultimately failed - leaving the personal computer OS business to Microsoft.
The overall personal computer business (and by default Windows) finally got an unintended boost as a result of an odd hangover from the earliest days of computing: The so-called Millennium, or Y2K, problem. Because the earliest computer systems had data and processing capacities that are unimaginably tiny by today's standards, engineers had written a lot of code that only used the last two digits in the year. This problem was first reported as early as 1985 - but didn't become widely known till the late 1990s. This set off a worldwide buying binge among businesses, institutions, and consumers - with periodic warnings from computer industry professionals warning of the dire consequences if every computer and software package ever sold wasn't replaced with something that was "Y2K Compliant." People literally were worried that power stations would shut down and airplanes fall out of the sky. As it turned out, actual problems resulting from it were generally minor (ie. some slot machines stopped working, or weather maps had a wrong date on them.)
But by then the personal computer business had become the monster it is today, and Microsoft Windows was the unstoppable juggernaut that was going to rule the world. Meanwhile more and more people were starting to use the "Internet" and out in California Apple Computer was starting work on a portable music player called the "iPod."
The rest - as they say - is history.
