If there were no Microsoft? That's an easy one.
Computer users would have become smarter. Why? Because the technological advances demands that computers must be used. However, without the Windows GUI, then the alternative is to do it with the CLI. Which would make the users exercise their gray matter a bit more. Thereby, presumably, leading to healthier and fitter gray matter, resulting in smarter users. Development of software would probably have gone ahead by leaps and bounds, too, since there will be no copyright barriers and encrypted code to impede its progress. Eventually there would be some kind of GUI, I suppose, but more as a novelty than a necessity.
And, who knows, we might face the possibility of someone called Bill Gates running for President of the US of A. That Bill is one real smart cookie. If he had not applied himself to making money with Microsoft and Windows, he could have very well succeeded in another career and ended up running for public office.