Microsoft had 90%+ of desktop penetration in 2008; in fact, it made news that it had slipped to below that at the end of 2008.[0][1]
Now it's around 70%, but seems to be improving?[2]
[0]: https://www.osnews.com/story/20605/windows-market-share-slip...
[1]: https://www.computerworld.com/article/1367310/windows-market...
[2]: https://www.statista.com/statistics/218089/global-market-sha...