The 19 U.S. states that are working with the federal government to bring Microsoft up on antitrust violation charges say that only the strictest measures against the company will be acceptable, should the company be found guilty. These measures include a total breakup of the Microsoft or, at the very least, the licensing of the Windows source code so that other companies can market and sell Windows-compatible operating systems. But the states aren't stopping there: They will also likely attempt to fine Microsoft individually for every single antitrust violation they can find. This could easily result in millions of dollars in fines.
And should Microsoft be broken up, it's likely that three or four new companies would be formed, perhaps along the lines of different businesses (operating systems, applications, Internet, and the like) or perhaps nearly identical companies that would market essentially the same products, thereby maintaining competition