Firms continue to produce (illegally) counterfeit computer software and documentation. Some of the illegal copies are Microsoft products, though Microsoft still has a large share of the market for its products. The presence of enforced copyright protection laws indicates that the market for Microsoft software cannot be considered a competitive market because:

There are significant barriers to entry

Explanation:

Base on the scenario been described in the question, other firms that were producing counterfeit software are not going to make the market of Microsoft competitive because, the products are illegally produced and Microsoft has enforced the presence copyright protection laws serves a barrier to firms producing counterfeit software.