"We made an offer, we made another offer, and it was clear that Yahoo didn't want to sell the business to us and we moved on," Ballmer said. "We are not interested in going back and re-looking at an acquisition. I don't know why they would be either, frankly. They turned us down at $33 a share."

Yahoo shares last traded at $13.96 on the New York Stock Exchange.

Yahoo chief executive Jerry Yang said Wednesday that Microsoft should make another bid for his company, which runs the world's No. 2 search engine. His appeal came after top search engine Google backed out of an Internet advertising partnership to avoid a challenge from the U.S. Justice Department, which said it would sue to block the Yahoo deal to preserve competition in Internet advertising.

Yahoo had been counting on the Google Inc. deal to boost its finances and placate shareholders still incensed by management's decision to reject the $47.5 billion takeover bid from Microsoft six months ago.

"I'm sure there are still some opportunities for some kind of partnership around search, but I think acquisition is a thing of the past," Ballmer said.

"Everybody needs a good competitor, and we just want the other guys in this business to have a good competitor that they have to think about every day," he said.

He also told the audience that Microsoft saw an opportunity to reinvent the online search process.

"If anybody thinks the future of search is going to look like the present search, that's crazy," Ballmer said. "The user interface on search hasn't changed for six years. You still get the same dull, boring ten blue links for God's sake. Can't we do any better than that?"