A testy and fidgety Microsoft Corp. Chairman Bill Gates made another electronic appearance at the antitrust trial of his company yesterday, giving answers that were alternately combative and forgetful as he fielded questions in a videotaped deposition about rival Internet software products.

His responses, which included quibbles about the definitions of such words as "concerned" and "compete," prompted the judge hearing the case to chortle and shake his head in disbelief.

In an hour of videotaped clips played in the courtroom by the government, Gates frequently responded to questions by saying he did not know the answer. He said he could not recall sending any of several electronic-mail messages bearing his name that were placed before him. When asked to read the messages, Gates testified that he could not specifically remember writing them.

The tape played yesterday was the fourth video presentation of the world's richest man squirming under questioning since the trial began. Federal and state antitrust enforcers intend to show clips of Gates, who they are trying to cast as the orchestrator of Microsoft's alleged anti-competitive business practices, before each government witness.

Microsoft officials say that Gates responded in the same way that any company leader would in a similar situation, trying to focus questions so that he could give precise answers.

In one 20-minute segment, the government lawyer conducting the deposition, David Boies, focused on Gates's comment in a January 1996 e-mail that "winning Internet browser share is a very very important goal for us." Boies asked Gates whether his comment about "browser share" referred to wresting market share from other firms that were making software that people use to "browse" the global computer network, specifically Netscape Communications Corp.

But Gates answered that "the sentence doesn't appear to directly or indirectly refer to any other companies."

Boies tried again: "My question is, what non-Microsoft browsers were you concerned about in January of 1996?"

"I'm sure -- what's the question? Is it -- are you asking me about when I wrote this e-mail, or what are you asking me about?" Gates queried back.

"I'm asking you about January of 1996," Boies said.

"That month?" said Gates.

"Yes, sir," said Boies.

"And what about it?" continued Gates.

"What non-Microsoft browsers were you concerned about in January of 1996?" Boies tried again.

"I don't know what you mean, concerned,' " Gates said.

"What is it about the word concerned' that you don't understand?" Boies asked in incredulous tones.

"I'm not sure what you mean by it," Gates maintained, which prompted most people in the courtroom -- U.S. District Judge Thomas Penfield Jackson included -- to start snickering.

Finally, 15 minutes into the line of questioning, Gates said that the "non-Microsoft browsers" that concerned him included Netscape's Navigator product and one developed by America Online Inc.

When Boies had finished playing the tape, Jackson asked him: "How long did this deposition take?"

"Three days," Boies replied.

The government, which alleges that Microsoft's tactics to distribute its browser have violated antitrust laws, played the deposition clips as an introduction to its first expert witness -- Glenn Weadock, a computer consultant.

A Microsoft spokesman argued on the courthouse steps that the day's segments have no relevance to the case. "The government is simply trying to use Bill Gates's testimony to inject some life into their failing case," spokesman Mark Murray said.

Government lawyers contend that Gates's recollections -- or lack thereof -- about the company's browser strategy were a relevant prelude to the testimony of Weadock, who has said that many large corporations do not want browsing software included in Microsoft's dominant Windows operating system. "What the chief executive of Microsoft said about that subject is relevant," Boies said outside the courthouse.

The government argues that Microsoft's strategy of using the monopoly power of Windows to distribute its browser violates antitrust laws and hurts rivals such as Netscape.

After the Gates video presentation, a Microsoft lawyer spent the rest of the day cross-examining Weadock. The lawyer, Richard C. Pepperman II, suggested that Weadock had insufficient technical knowledge to provide meaningful opinions about Microsoft's inclusion of a browser in Windows.

Weadock conceded that his survey of the businesses was not "scientifically accurate," but he called his testimony "an illustration" of the views of many companies. The witness maintained that Microsoft could, if it wanted, provide computer users with the ability to easily block access to its browser in Windows 98.

The government's next witness is John Soyring, an executive at International Business Machines Corp., who could take the stand as early as this afternoon. In preparation for his testimony, government lawyers gave the judge several dozen documents that detail personal computer makers' frustrations with Microsoft. Among the documents are letters from Hewlett-Packard Co., Dell Computer Corp. and Gateway 2000 Inc. asking Microsoft to relax its rules governing the series of screens a user sees when a PC is turned on for the first time. In 1997, Microsoft told PC makers that users would have to see registration screens for Windows before anything else the manufacturer wanted to show. The government alleges that the requirement violates antitrust laws.

"From the consumer perspective, we are hurting our industry and our customers," John Romano, HP's research and development manager, wrote to Microsoft. "This situation must change. We find Microsoft control over our Customer's Out of Box experience totally unacceptable."