Windows 95 was too fat to install itself so needed help from the slimmer 3.1

30 years on, Microsoft engineer explains why the old OS had to babysit its flashy successor

Veteran Microsoft engineer Raymond Chen has answered the question of why Microsoft insisted on running up a miniature Windows 3.1 rather than a diminutive Windows 95 to install the full-fat version of the latter.

The reason? A combination of time, reboots, and size.

It is 30 years since Windows 95 graced computers around the world, and in 2024, Chen went into detail on the hows and whys of the operating system's setup process. If a user ran from MS-DOS, a stripped-down version of Windows 3.1 was installed, and a 16-bit Windows application would take care of copying files and migrating settings before firing up Windows 95.

If you started from Windows 3.1, you would go straight into that 16-bit app. But why bother with Windows 3.1 at all? Why not jump straight into a miniature Windows 95 to get the bulk of the setup done in a fully 32-bit operating system?

"I guess you could do that," said Chen, "but there are problems with that design, both from an engineering and a user experience standpoint."

From an engineering standpoint, going down the Windows 3.1 route was the easier path; Microsoft already had a miniature version of the operating system ready to go. Windows 95, on the other hand, "was notoriously behind schedule." Adding an extra task, such as "develop a variant of Windows 95 for the sole purpose of running Setup," would have attracted what Chen diplomatically called "pushback," although we can imagine some of the choicer words from engineers tasked with making Microsoft's 32-bit dream a reality.

That isn't to say it's not possible. Curious minds in subsequent years have managed to reduce the footprint of Windows 95 to 5 MB or less – an impressive feat – but still a considerable chunk larger than the comparatively svelte version of Windows 3.1 that Microsoft ultimately used.

Cutting Windows down to size continues today, with the likes of Nano11 ruthlessly slicing the bloat from Microsoft's current flagship operating system.

The next issue was one of user experience. First, even assuming Microsoft was able to shrink Windows 95, it would still require at least two floppy disks for installation, compared to the single disk needed for Windows 3.1. And then there were the reboots, of which two were required – one to boot into the mini-Windows 95 and a second to boot into Windows 95 proper.

"Which breaks the 'only one reboot' principle," said Chen, much to the amusement of anyone today who has had to watch a Windows device undergo multiple restarts after an update looked at it funny.

But those were different times, when Microsoft cared more about the user experience than trying to cram AI down people's throats at every opportunity.

"The preferred workflow would be to get the user quickly to the point where they are answering questions about how they want Windows to be installed, and then go off and do the work and then finish in Windows 95 with a single reboot," Chen explained.

A 30-year-old question answered: why not create a miniature version of Windows 95? Because Microsoft had already done the work with Windows 3.1. There was almost no engineering cost involved. And fewer reboots meant happier users.

Those were the days. ®