Microsoft is starting its long-anticipated drive into the consumer health care market by offering free personal health records on the Web and pursuing a strategy that borrows from the company’s successful formula in personal computer software.

The move by Microsoft, which is called HealthVault and was announced today in Washington, comes after two years spent building its team, expertise and technology. In recent months, Microsoft managers have met with many potential partners including hospitals, disease-prevention organizations and health care companies.

The organizations that have signed up for HealthVault projects with Microsoft include the American Heart Association, Johnson & Johnson LifeScan, NewYork-Presbyterian Hospital, the Mayo Clinic and MedStar Health, a network of seven hospitals in the Baltimore-Washington region.The partner strategy is a page from Microsoft’s old playbook. Convincing other companies to build upon its technology, and then helping them do it, was a major reason Windows became the dominant personal computer operating system.

“The value of what we’re doing will go up rapidly as we get more partners,” said Peter Neupert, the vice president in charge of Microsoft’s health group.