SAN FRANCISCO (Reuters) -- Microsoft 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 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.

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.

During a speech in Los Angeles, Gates said 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.

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