In the contemporary tech landscape, Microsoft stands as a paragon of industry giants, where even its less - popular offerings manage to rack up respectable sales figures. Yet, back in the mid - 1980s, Microsoft's foothold in the market was far from unshakable. It was during this era that the company unveiled what would go down in history as its worst - selling product: an operating system dubbed 'OS/2 for Mach 20'.

In the mid - 1980s, the personal computer realm was undergoing a seismic shift. These devices were evolving from specialized tools used by professionals into mainstream consumer goods, with technology advancing at a breakneck pace. To cut costs, many companies resorted to boosting the performance of older machines by installing accelerator cards.

Microsoft stepped into this arena with its Mach series of accelerator cards. Among them, the Mach 20 stood out for its superior performance. It also had the capability to support the connection of secondary cards for memory expansion. However, the sales of the Mach 20 were far from impressive.

Despite this, Microsoft went ahead and developed a specialized version of the OS/2 operating system specifically for the Mach 20. OS/2 was the result of a collaborative effort between Microsoft and IBM. It had earned a certain level of respect within the tech community, but its user base remained relatively small.

The combination of a niche operating system and niche hardware proved to be a recipe for disaster. 'OS/2 for Mach 20' was essentially shunned by the market. Globally, only 11 units were sold. To make matters worse, 8 of those units were returned, leaving a meager 3 actual users in the end.