Microsoft claims 4m Windows 8 upgrades so far

Microsoft chief executive Steve Ballmer said the company has sold 4 million upgrades to Windows 8, signaling a strong start for its new operating system which launched on Friday.

Ballmer, speaking at a meeting for software developers at Microsoft's headquarters near Seattle, said hundreds of millions of Windows systems would be sold over the next year, and the company was seeing strong interest from business users.

Ballmer already said on Monday that Windows 8 was outselling the previous version, Windows 7, at the same stage after launch three years ago.

"We're seeing preliminary demand well above where we were with Windows 7, which is gratifying," Ballmer said yesterday.

Windows 7 is the best-selling version of Windows so far, selling more than 670 million licenses in three years since release in 2009.