The estimate, offered by an accountant testifying for Bristol, assumes Bristol's Wind/U software product would be bundled with computers sold by major manufacturers.
A Microsoft spokesman called the figure "pie in the sky," noting that Bristol has not stuck any such deal to date.
Danbury, Connecticut-based Bristol sued Microsoft last August, alleging that its refusal to offer Windows NT code on the same terms offered in a previous license violated antitrust laws. Bristol, whose Wind/U allows certain Windows NT functions to run on Unix platforms, needs the Microsoft code in order to make the product.
Bristol alleges that Microsoft offered unfavorable licensing terms after the Bristol software became a threat to NT. The suit seeks an injunction requiring Microsoft to turn over the source code and to pay damages.
Henry Stotsenberg, the accountant testifying for Bristol, said today that if computer sellers had bundled Wind/U with the machines they sold, damages stemming from Microsoft's licensing demands would reach $263 million, people on both sides of the case said. Later in the day, Bristol executive Jean Blackwell testified that Microsoft reneged on its promise to participate in a partnership referred to as the Windows Interface Source Environment, or WISE, in which it would help "port" Windows NT code to Unix platforms.
Blackwell, the last witness to testify on Bristol's behalf, is expected to wrap up her testimony tomorrow. Microsoft will then open its defense by calling senior vice president Jim Allchin to the stand. He is expected to testify that the WISE program has increased competition and innovation in the workstation market. Microsoft will have 12 court days to present its case.
With the case hitting the half-way mark, the companies differed sharply over how the trial had gone.
"We are ecstatic with how our part of the case has gone so far," said Bristol chief executive Keith Blackwell. A highlight of the case, he added, is evidence that shows Microsoft wanted to use WISE to kill the competitive threat posed by Sun's Java programming language.
But Microsoft spokesman Tom Pilla said the company has successfully chipped away at Bristol's case, getting two of its five claims dismissed. Most recently, Pilla said, Microsoft won a motion to dismiss claims that Microsoft source code was an "essential facility" to Bristol's doing business.
"We've said all along the facts would come out at trial," Pilla said. "So far, you've seen some very important information coming out in favor of Microsoft's position."
Pilla went on to criticize the estimates of Stotsenberg, the Bristol accountant, saying they directly contradicted figures offered by an economist who testified for Bristol earlier in the case. Whereas Stotsenberg claimed the market for Unix products was healthy, the economist said the industry was dying off because of Microsoft's monopoly, Pilla said.
After Microsoft presents its case, both sides will have the chance to call rebuttal witnesses and make final arguments. The trial is expected to finish by the end of July.