Wow you could not be more wrong, but it is ok, i forgive your ignorance. MS is not a monopoly, their are plenty of alternatives (Mac OSX and Linus for example). It is not the fault of MS that they have the best product and the largest share of the computer market. Maybe if owning an Apple was not so obscenely expensive their share would be higher.
Microsoft was found guilty of being a monopoly. They eventually had to settle. Microsoft did things like purposely degrading the operation of third party software that competed with them, and tied products (which you cannot do if you have monopoly market power). They are a legal monopoly (you seem to think to be a monopoly there has to be no competition. That is not the legal definition - we aren't talking oligopoly vs. monopoly like in economics).