No doubt you've heard the basic argument. Microsoft controls the core of the software business. It's now targeting digital content.
Content is a lot like software.
Ergo,Microsoft is poised to dominate electronic content. Software is actually very different from content, and success in one doesn't imply success in the other. These bits can be reproduced, legally or illegally, with effectively zero marginal cost. In economic jargon, software and content have virtually infinite economies of scale. But economics is where the big similarities end.