Microsoft has sold nearly 40 million copies of Vista, its new operating system replacing Windows XP.
Microsoft is counting on Vista to drive its future sales growth
According to chairman Bill Gates, sales had been quicker than Microsoft had expected. Windows is used on more than 90% of the world's personal computers.
Vista has been on sale to consumers since 30 January, and there had been concerns that take up might be slow, hurting profits.
"I'm really thrilled at how this has come together," Mr Gates said.
Speaking 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.
Vista is Microsoft's first new operating system in five years, and the company said that more than three quarters of its sales have been for the software's premium versions.