The case centres on Microsoft's allegedly illegal business practices to discourage competition, and the way it used its dominance of the operating system market to gain competitive edge in the market for Internet browsers.
Microsoft argues it did nothing illegal, and that its business practices were normal and fair competition. The trial in Washington has been going for four months so far.
Although the US Justice Department has discouraged speculation about the outcome, one possibility would be to divide the company into two or three, the Washington Post reported. This could have huge implications for the software market.
Under one solution, the company's Windows operating system, the most common operating system for personal users, could be made a separate company. Under another, Windows might be hared among several companies.
"Speculation about what the department might do if the court rules in our favour is premature and inappropriate," said a Justice Department spokesman.
Another possibility is the company could be forced to stop certain business practices, and required to licence key technologies, such as Windows to competitors.
Microsoft is halfway through its defence, which is not thought to have gone as well as the company might have hoped.
"Most observers believe the odds are high that the judge will rule against Microsoft ," the Post reported.