Microsoft has sold nearly 40 million copies of its new Windows Vista operating system, chairman Bill Gates said yesterday.

Gates said sales had been better and quicker than expected, making Windows Vista Microsoft's quickest selling software.

"I'm really thrilled at how this has come together," Gates said at the Windows Hardware and Engineering Conference ( WinHEC ) in Los Angeles.

"As of last week, we've [sold] nearly 40 million copies," Gates said in his keynote speech . "That's twice as fast as the adoption of Windows XP, the last major release we had."

More digital media

One of the key reasons for the strong sales is that many customers are increasing the amount of digital media they use and store, Gates said. The ability to manage digital media is a key feature in Windows Vista. The aim is to simplify the process of sharing digital content such as photos, videos, music and documents.

Gates also announced new partners for its Windows Home Server product. These include Gateway , LaCie and Medion . Microsoft has already said that HP will launch home servers based on the technology later on this year.

"This will come out in the fall," Gates said. He added that smaller computer makers will also be able to build products based on Windows Home Server. Microsoft is marketing the product as a central home server for media such as photos, movies and music. It's also being touted as a seamless way to back up PCs in the home.

Vista release

Windows Vista was released on 30 January, replacing the previous Windows XP operating system. Windows is used on more than 95 per cent of computers worldwide.

Microsoft said more than three quarters (78 per cent) of Windows Vista sales have been for the Premium versions of the operating system.

Microsoft also said that for every dollar it makes of Windows Vista and Windows Server 2008 (previously known as Longhorn), other technology companies will take $18. A Microsoft-sponsored IDC study found that "as many as 200,000" other companies will sell more than $120 billion worth of products and services designed for the two Microsoft operating systems by the end of 2008.