Microsoft is counting o­n Vista to drive its future sales growth

Mr Gates said sales had been quicker than Microsoft expected, and made Vista the firm's quickest selling software.

Vista was released o­n 30 January to replace the Windows operating system, and there had been concerns that take up may be slow, hurting profits.

Microsoft's operating systems are used o­n more than 90% of the world's PCs.

"I'm really thrilled at how this has come together," Mr Gates said at a company conference in Los Angeles.

He added that o­ne of the reasons for the strong sales was that many consumers were looking to increase the amount of digital media they used, a central feature of the Vista package.

The software aims to make it easy for consumers to set up home computer networks, and to manage and share digital content such as photos, videos, music and documents.