Not so, Blakewry!
It is precisely because of their market share that Microsoft is evil. All monopolies (and, for that matter, all quasi-monopolies) are evil, almost by definition. Off the top of my head, I can't think of a single privately-owned monopoly that was not evil, and quite a few of those owned by the public as well. (Can we say "Telstra pre-selloff"?) (Not that the post-sellout Telstra is any better: which only goes to illustrate my point that it is not the nature of the company qua company that matters, it is the type of behaviour that is forced upon it by the distorted non-market structure it is operating within.)
Do I think Bill Gates and his accomplices would be nice, honest, decent, trustworthy businesmen if their company had a market share of, oh, say 20%? Not a chance: we know from the facts of history that he is a nasty bit of work, and that his cheating, disloyalty and dishonesty started way before he became Mr 95% of the Market.
But the point is, if MS had a 10% or 20% market share in a competitive free market, it would not really matter, because if you objected to one aspect or another of their business ethics, you could simply spend your money with one of the other companies. Exactly the same logic applies to every other company in every other field. The economic magic of capitalism can and does only function when the fundamental base conditions it requires are met, and the most fundamental base condition of them all is a thing called a "market". A market, by definition, has many buyers and many sellers.
Everything else is crap.
The whole idea of capitalism (or "free enterprise" if you prefer, the two terms mean exactly the same) is that the government does as little regulation as possible, because a free market is almost always a better, more fair, and more efficient way to allocate resources and share out benefits than any other way so far invented. But it only works, can only work, when there is a functional market.
Without a freely comptitive market, you have only two realistic possibilities: facisim or communisim. Neither is a nice way to live. And, as it happens, neither is (generally speaking) very good at maximising resources and providing sustainable economic growth.