Google, he said, has acquired companies and then made their products free, roiling the markets in which they compete. Google has introduced free versions of the graphics software made by SketchUp and of the Internet analytics service from Urchin, two companies that it bought. And Google won a bid to offer wireless Internet service in San Francisco at no charge, hoping to make money by selling local advertising. If this model proves to be successful, it could cut into the business of other Internet providers and wireless phone companies. Now Google is starting to move directly into Microsoft's core market. It recently acquired Writely, a Web-based word processor. How far Google can eat into Microsoft's software franchise is uncertain. But Microsoft fears that Google could become a kind of operating system of the Internet in the same way that Windows is the dominant operating system of personal computing.