A federal judge in Seattle has decided that Microsoft CEO Steve Ballmer has to testify in a class action lawsuit against Microsoft. The lawsuit states that the company misled consumers in a marketing campaign for its Windows Vista OS in which computers sold with an older Microsoft operating system were labeled “Vista Capable”, even if they could only run a basic version of Vista. Judge Marsha Pechman of the U.S. District Court for the Western District of Washington at Seattle ruled that Ballmer has personal knowledge about the facts surrounding the case and its information might help. This was announced through court documents released late Friday.

The lawyers will have a maximum of three hours to take a deposition from Ballmer at the time and place of his convenience, and the deposition must take place within 30 days of the order. The case against Microsoft was launched early last year, and it seems that most computers labeled “Vista Capable” in the marketing campaign, which began in early 2006, cannot run or run poorly Vista Premium, the version of Vista with the most popular features. However, Microsoft representatives told the court that Ballmer was not involved in operational discussions around the “Vista Capable” program and offered co-president Jim Allchin and senior vice president Will Poole instead of Ballmer, stating that the two had superior knowledge of the program.

The plaintiffs won the argument to question Ballmer by pointing out conversations between Ballmer and Intel CEO Paul Otellini in which the two discussed possible changes in the Vista Capable requirements. Microsoft denied the allegations in the lawsuit, saying that although the Home Basic version lacked some features found on premium editions of Windows Vista, it was still part of the Vista family. The case is set to go on trial in April next year.