Niiiiiiice article by The John Markoff:

This week, [Microsoft] plans to turn that strategy upside down, making available free software that connects its Windows operating system to software services delivered on the Internet, a practice increasingly referred to as "cloud" computing. The initiative is part of an effort to connect Windows more seamlessly to a growing array of Internet services.

The strategy is a major departure for Microsoft, which primarily sells packaged software for personal computers. With this new approach, Microsoft hopes to shield its hundreds of millions of software customers from competitors like Google and Salesforce.com, which already offer software applications through the Internet.

Software via the Internet: Microsoft in 'Cloud' Computing - New York Times