Microsoft is preparing to go to court in Minnesota next week to fight allegations that it abused its Windows monopoly to overcharge customers in the state for its software. As part of its defense, Microsoft may call Bill Gates and Steve Ballmer to testify, the company said Friday.Unless a last minute settlement is reached between the software vendor and lawyers representing Minnesota consumers, opening arguments in the case are scheduled to begin the midweek, Microsoft spokesman Jim Desler said Friday. The court has allotted three months for the trial, he said.The Minnesota case is one of four class-action lawsuits brought on behalf of consumers against Microsoft that the Redmond, Wash., company has been unable to settle or get dismissed. Similar cases in Arizona, New Mexico and Iowa could also be headed for trial, Desler said."In other states we were able to reach settlements that were reasonable and we were simply not able to do that here and therefore are going to trial," Desler said of the Minnesota case. "This is a case that deals with the question of whether or not Microsoft engaged in anti-competitive conduct and if so whether or not it overcharged customers."In the settlements reached with lawyers representing consumers in states including California, Tennessee, North Dakota, South Dakota and Kansas, Microsoft agreed to make vouchers available to customers who bought Microsoft software during a specific time period. The vouchers can be used to buy computer software or hardware.As part of the settlements Microsoft has always denied any wrongdoing. In the Minnesota case it also maintains that it did not violate any laws. "We believe the plaintiffs' claims are wrong and based on unjustified calculations. We're confident in the merit of our positions and that the plaintiffs will not win their case," Desler said.If the case goes ahead as planned, lawyers representing Minnesota software buyers will be the first to present their case. Microsoft is not expected to present its defense until April, Desler said.As part of its defense, Microsoft has compiled a list of witnesses it may call. The list contains 35 names, including Chairman and Chief Software Architect Bill Gates and CEO Steve Ballmer. "Not all these witnesses will be called," Desler said. "The decision on who will be called will be made during the proceedings."