US district court judge Colleen Kollar-Kotelly begins a hearing today on the proposed settlement authored by the US Department of Justice.
Federal law requires the judge to decide whether the proposed settlement is in the "public interest".
This settlement hearing, expected to last a couple of days, will be followed by a remedy hearing that may last as long as two months.
This remedy hearing will focus on nine states' proposal to seek such things as a stripped-down operating system.
Kollar-Kotelly is allowing testimony from 16 witnesses for the states and 31 for Microsoft. The judge is giving each side 100 hours to make their respective cases.
Bob Lande, a law professor at the University of Baltimore Law School said: "It shows that she is taking the remedy phase very seriously. She is erring on the side of being absolutely fair to Microsoft."
The remedy hearings are scheduled to begin March 11, but Microsoft has asked the judge for a two-week delay to give it more time to analyze revisions to the states' proposed remedy