Microsoft CEO Steve Ballmer has previously stated he had no knowledge of the whole “Vista Capable” fiasco, in which the company apparently lowered the minimum requirements to run Vista in order to help Intel sell their motherboards with embedded 915-based graphics chipsets, but a federal judge wants him to testify in an ongoing class action case anyway.

Apparently, the judge is curious as to what was discussed in a phone call between Ballmer and Intel CEO Paul Otellini on January 30, arguing the Microsoft exec may have “unique personal knowledge of relevant facts.” Ballmer has 30 days to meet with plaintiffs’ lawyers for his deposition and will be forced to testify when the case goes to court next April.