Microsoft never had 90% of the "operating system" market. They had 90% of the "desktop operating system" market.

What marketshare does iTunes have in "phone synchronisation software"? Carefully define your market and you can probably find a monopoly.

That's kind of like saying if a car company owned 95% of the market, they wouldn't be a monopoly becuase you can always just ride a bike.

That really sounds like a distinction without a difference. MS had control of 90% of consumer and office computing. True? Apple doesn't control anywhere close to that in phones.

I disagree with your premise that embedded devices and servers don't matter.

My premise is that embedded devices and servers don't matter to the vast majority of people who use computers, then and now.

If you're a home or office user, you can't use a server to do your work. You can't use an ATM to do your work. You can't really be pretending the desktop computer market is some narrow or obscure thing, can you?

In 1998, as a home or office user, you had a very specific set of choices for computing tasks, of which Microsoft controlled the vast majority.

Servers, embedded devices and PCs are totally different markets.