Microsoft Chief Executive Steve Ballmer has been ordered to testify in the Windows Vista Capable suit. The suit alleges that Microsoft modified the Vista Capable marketing program to help Intel Corp sell hardware that would soon be obsolete.

Ballmer must be deposed within 30 days as part of the class-action lawsuit. US District Court Judge Marsha Pechman ruled on Friday that Ballmer may have unique personal knowledge of relevant facts.

The personal knowledge in question is about a phone call Ballmer had with Intel CEO Paul Otellini in January 30, 2006. It is the same day Microsoft decided to make a major change in its Vista Capable program. The change would help Intel and PC makers sell hardware that would be obsolete after the launch of Windows Vista.

Vista was delayed until January 30, 2007. The PC industry was concerned that sales would dry up as consumers waited for the new Microsoft operating system.

Intel was informed by Microsoft in January 2006 that it was moving its Vista Capable. The Windows program was changed from June 1 to April 1. However, Intel asked Microsoft to stick to the original June start date so that PC makers could have more time to sell hardware that did not meet Vista requirements.