On April 3, 2000, a U.S. federal court ordered that Microsoft be split up. As a result of an antitrust suit filed in 1998 by the U.S. Justice Department, Judge Thomas Penfield Jackson ordered that Microsoft be broken up into two companies: one that would develop and sell operating systems, and another that would handle other types of software.

This followed Jackson's Nov. 5, 1999, in which he declared Microsoft a monopoly that used its power to attempt to destroy perceived threats from competing companies, including Netscape, Apple, Sun, Lotus and others. The court's breakup order .

This one's a toss-up between two very big decisions. First up is a $5.5 billion suit filed in 1988 by Apple against Microsoft and Hewlett-Packard alleging that Windows violated the "look and feel" of the Mac operating system. Over the years, the lawsuit was whittled down by a variety of courts, and on June 1, 1993, Federal District Judge Vaughn Walker and in Microsoft's favor.

That was certainly a significant decision, but it ultimately would not have affected the way in which Microsoft did business -- Microsoft could have simply paid Apple royalties and continued on its merry way. An even more important decision for Microsoft happened on June 28, 2001, when the Judge Thomas Penfield Jackson's 2000 .