There can be arguments made on both sides of this issue.
Most people would tend to say that Microsoft’s monopoly is bad for the consumer. This is the case because monopolies have the power to charge excessively high prices for their goods and services. They do not fact serious competition and therefore have no great incentive to decrease their prices. They might also stifle any competitors and deprive us of our potential ability to benefit from things they would have created.
However, it is possible to argue that this monopoly power is somewhat beneficial. Because Microsoft has so much of the market, it ensures that all of our devices and programs will work with one another. This might not be the case if there were many different operating systems being used. The standardization that is brought about by Microsoft’s monopoly power is beneficial to us because it creates a situation in which our computer systems are easily integrated with one another.