Popular electronics stores would do a in-store setup of your computer before you left with it. Part of this involved entering the users name and windows key.

I probably used the same key to setup over 1000 PC's when I worked there.

'Back in the day' regular formats were a pretty good way of maintaining system performance. They still are really but computers being an order of magnitude overpowered for all the tasks 90% of users do makes it less relevant. You'd be surprised how easy it is to memorize long series of digits when you enter them a few times. For instance FCKGW. Who was the president in 2001? You'll now literally never forget those 5 letters.

That was the first thing I thought of at the beginning of this thread.

It was the first consumer NT-based Windows, the first with activation and this key, which let you bypass all that, was out before the OS was officially released.