Microsoft lawyers this week locked horns with key government witness Edward Felten, the Princeton computer professor who last year testified that Windows suffered "performance degradation" when Internet Explorer was unbundled.
Felten is one of three key rebuttal witnesses who have been called by the government to strengthen its case against Microsoft as the US government's long-running anti-trust case against inches towards a conclusion.
Microsoft lawyer Steven Holley sought to cast doubt on Felten's testimony by making him repeat his demonstration of the unbundling program, shown in court last year, that appeared to show the Explorer and Windows were inseparable.
The US government has argued throughout the trial that Microsoft bundled Explorer with Windows in an attempt to block out rival browser vendor Netscape Communications.
However, after the repeat performance was unsuccessful, Felten argued that his program was a prototype and could have been affected by other software running on the new trial machine.
Felten also came in for questioning from presiding federal court judge Thomas Jackson, who asked him about the security implications associated with the use of Web browsers.
Felten's testimony followed damning evidence from senior IBM executive Garry Norris, who earlier in the week outlined the 'carrot and stick' tactics which he claimed Microsoft used to convince IBM to promote Windows 95 exclusively.
While Microsoft's lawyers argued that it did not specifically demand IBM abandon its own rival product, OS/2, the conditions of the licensing agreement Microsoft offered IBM for Windows 95 amounted to the same thing, Norris, the former director of software strategy and strategic relations at IBM, argued.
"The effect in the marketplace when you advertise another manufacturer's products only, when you have a competing product in the marketplace, sends a message to your customers that they are promoting and advertising Windows 95 only. They must not be promoting or shipping OS/2," Norris told the court.
Microsoft has named Massachusetts Institute of Technology academic Richard Schmalensee; Oblix chief executive Gordon Eubanks; and AOL senior vice president David Colburn as its rebuttal witnesses.
The latter will appear as a hostile witness and Microsoft is expected to allege that he kept AOL's takeover of Netscape secret in order to help the government's case, earlier in the trial.
After the rebuttal phase, which is expected to finish early next month, both sides have 30 days to submit proposed findings of fact to Judge Jackson.
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