Microsoft chairman Bill Gates has revealed that Redmond has sold more than 100 million licences of Windows Vista since its launch 13 months ago.

Speaking at the Consumer Electronics Show, Gates announced the 100-million mark during his keynote address.

The last time Microsoft trotted out Vista numbers was in October, when it claimed that it had shipped 88 million copies of the operating system. Previously, it had cited 20 million copies shipped in its first month after launch, 40 million copies in the opening 100 days and 60 million by late July.

Back in November, Forrester Research revealed that businesses were continuing to avoid Vista. The researcher said that continued loyalty to Windows XP remained a bigger hindrance to Windows Vista sales than Mac OS X and Linux. The US government's Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF), said last year that it may stick with Windows XP for up to three more years.

Gates didn't specify whether the 100 million excluded corporate licences, but simply said: "One hundred million people are using Vista now." When Microsoft claimed 88 million two months ago, it said the number didn't take into account copies available or sold to businesses via volume licensing deals.

Vista has also battled underwhelming demand from consumers.

According to measurements collected by Net Applications, which monitors traffic at approximately 40,000 websites, Vista's share broke the 10 percent mark for the first time, to end the year at 10.5 percent. In comparison, Windows XP accounted for 76.9 percent and Mac OS X's 7.3 percent during December. (Read why 2008 will be the real year for Vista's first revision SP1, on John E. Dunn's blog, here.)

Based on original reporting by Gregg Keizer, Computerworld (US online).