Microsoft has moved to counter criticism about the uptake of Vista by announcing that it now has shipped 60 million copies of the OS.

"By our math, we eclipsed the entire installed base of Apple in the first five weeks of shipment," Kevin Turner, Microsoft's COO, said at the company's annual financial analysts meeting.

Turner said there were 42 million PCs covered by volume-licensing annuity agreements for Vista. He said strong renewals for enterprise agreements were driving the uptake. "Customers are purchasing the rights to Vista because they are planning deployments," he said.

He said Continental Airlines planned to roll out 10,000 seats of Vista by year-end, and Banco Bradesco in Brazil had rolled out 70,000 seats this year. Microsoft itself has rolled out 100,000 seats.

He said deployments were being driven by corporate rollouts, governments and mid-market customers.

Microsoft said its Windows installed base will reach another milestone in the next 12 months.

"The installed base of Windows computers this coming 12 months will reach one billion," said Steve Ballmer, Microsoft's CEO. "If you stop and think about that for a second, by the end of our fiscal year '08 there will be more PCs running Windows in the world than there are automobiles, which to me is kind of a mind-numbing concept."