By Sue Zeidler

LOS ANGELES (Reuters) - Microsoft Corp. has sold nearly 40 million Windows Vista licenses in the first 100 days that the latest version of the operating system has been available, Chairman Bill Gates said on Tuesday.

Gates said an accelerating consumer shift to digital lifestyles had helped make the operating system the fastest-selling in history, and that premium editions have accounted for 78 percent of Vista sales.

" I' m really thrilled at how this has come together," said Gates during a speech at Microsoft' s Windows Hardware Engineering Conference 2007 in Los Angeles.

Windows operating systems run on more than 95 percent of the world' s computers and represent the Redmond, Washington-based company' s biggest profit driver.

Vista, which Microsoft introduced on Jan. 30, also marks the first major operating system upgrade in more than five years from the world' s biggest software maker.

Gates said Windows Vista allows many niche-oriented PC functions to move into the mainstream, from Web cameras to various home remote-controlled items.

Gates also said that the company named its next-generation Windows Server software -- formerly known as " Longhorn" -- Windows Server 2008.

Windows Server is the server operating system equivalent to the Vista PC operating system, with an emphasis on many of the same features, such as better security.

Microsoft, which controlled an estimated two-thirds of the global server software market in 2006, has said the product is on track to debut in the second half of 2007.

Gates said Windows Vista and Windows Server 2008 will provide a platform for hardware innovations and drive increased demand for a wide range of new PCs and devices.

He cited a study by research group IDC that projects there will be a $120 billion economic impact from product and services revolving around Windows Vista and Windows Server 2008.

The company also said three new hardware manufacturers -- Gateway Inc., Lacie and Medion -- plan to build products for Windows Home Server.

That software is aimed at helping families with multiple PCs easily centralize, share and protect digital content, such as pictures, music, documents and videos.

Microsoft shares were up 7 cents at $30.94 in afternoon Nasdaq trading.