Many missteps have already been made. Despite investing heavily in search engine technology over the years, Microsoft has watched Google steadily erode at its market share. This time it is taking a more precise approach, working to help searchers with specific online tasks.

Image For shopping searches, one of Bing's four "verticals," the service offers results that go beyond the 10 blue links of traditional search. The other verticals are travel, health and local.

Microsoft will back its latest release with one of the biggest marketing efforts in its history. And it has come up with a new name, Bing, that will replace the confusing Live Search.

The stakes for Microsoft are high. Search has become the central tool for navigating the Web, and ads tied to search results are becoming a more important piece of the advertising market.

Microsoft is so eager to catch up that it bid nearly $50 billion last year to buy Yahoo, the No. 2 search company behind Google. Mr. Ballmer said he was no longer interested in buying Yahoo, but still hoped the companies would team up to take on Google in search, and talks on a partnership are continuing.

For now, Microsoft is proceeding on its own. Bing represents more than a year of research showing that while users say they are generally satisfied with Web search services, their behavior suggests that they often stumble as they rely on searches to complete certain tasks.