Taking the stage at the Las Vegas CES (Consumer Electronics Show), Bill Gates announced that Windows Vista has sold 100 million copies, meaning that 12 million copies sold since last October.

He did not specify what the 100 million figure means, just saying, “one hundred million people are using Vista now.”

Windows Vista operating system is proving far less popular with new PC buyers than Windows XP did during XP’s first year on the market, if statements by company chairman Bill Gates at this week’s Consumer Electronics Show are any measure.

Gates, in Las Vegas Sunday, boasted that Microsoft has sold more than 100 million copies of Windows Vista since the OS launched last January.

While the number at first sounds impressive, it in fact indicates that the company’s once dominant grip on the OS market is loosening. Based on Gates’ statement, Windows Vista was aboard just 39% of the PC’s that shipped in 2007.