In general, Microsoft's shares have remained strong despite an ongoing investigation by the Justice Department and state attorneys general. Microsoft stock has traded as high as 99.13 and as low as 57.44 during the past 52 weeks.
Attorney General Janet Reno and Assistant Attorney General Joel Klein held a news conference at 9 a.m. PT to announce their federal lawsuit. A parallel action was filed by 20 state attorneys general and the District of Columbia, making it one of the largest antitrust cases in U.S. history.
As regulators proceed with their lawsuits, Microsoft is shipping its Windows 98 operating system to computer makers today. It plans to ship the software to retailers June 25.
Earlier this year, the surge in Microsoft stock pushed the company's market capital to more than $200 billion, making it the only other company besides General Electric in that category. However Microsoft is a "20-something" year-old company, while GE traces its roots to Thomas Edison in 1878.
The boom in Microsoft's stock also pushed chief executive Bill Gates's net worth to more than $50 billion. He is the nation's richest individual.