It’s worth more than $100bn at a conservative estimate. It has been the subject of lawsuits and scandals involving states, countries and continental communities. Plenty of people would love to see it destroyed. And on 20 November, Microsoft Windows reached the tender age of 21 years old.

Windows was born in 1985 when Starship topped the US charts with We Built This City and Feargal Sharkey had British toes tapping with A Good Heart, although Microsoft had been talking about it since 1983, sometimes referring to it by the catchy sobriquet of Interface Manager. It required DOS 2.0 and 256kB of RAM in exchange for which buyers got a graphical user interface and host of mini applications. Widely disparaged as a DOS front-end, the first release could only tile panes. Like any newborn, it couldn’t do much, had a lot of wrinkles and there was a lot of discussion of the, “Should that bit be there?” variety.

Version 2.0 arrived when Windows was two and beginning to do more interesting things. The key new feature was overlapping windows but other elements – minimise and maximise functions and using the ALT key for keyboard shortcuts – remain to this day.

The first version of Windows that I used was version 3.0, the 1990 release that was the first to be broadly pre-installed on PCs. Intel’s 286 was just giving way to the 386, and 1MB of RAM and a 20MB hard drive was a common configuration. Windows would reduce such a beast to pitiful disk-thrashing and reduce users to finger-drumming torpor but plenty of people saw the benefit of running Windows on a 386SX with 4MB.

Why? There was a lot of talk about memory management at the time but in reality Windows got big on plain ease of use. For the user accustomed to WordStar, 1-2-3 and dBase it was a glimpse of colour in Thatcher’s monochrome Britain. The ability to cut and paste chunks of text was heaven in those dark days of memorised keyboard combinations and imagining what printed documents might look like.

Users didn’t care about geeky discussions as to whether Microsoft had ripped off the Mac or Xerox’s prior art. They just knew that Windows was preferable to the character-based alternative they had been using.

DOS users clung for a while to their copies of XTree, Sidekick and QEMM but Windows quickly became the de-facto standard for office grunts. IBM’s appalling marketing of OS/2 helped: while a host of startups such as Corel and Micrografx boosted Windows with apps, a clueless Big Blue displayed a Britney Spears-like ability to maintain relationships. When it finally came up with its answer, OS/2 2.0 set users such a tough installation task that a costly battle for the business desktop was won easily by Microsoft.

Since then, Windows has gone through its awkward teenage years, most notably with the botched Me release, but its grip on client computing has hardly wavered. At 21, it is one of the business world’s most powerful franchises and a target to many. For OS/2 back then, read the competition from Linux and browser front-ends today, but as Windows continues to morph it is unlikely to leave us anytime soon.