Windows Vista will have sold more copies than Windows XP during its first year on the market, but according to a report by InformationWeek, Microsoft's new operating system is still not as widely adopted as its predecessor. The publication bases its assertion on a statement by Microsoft Chairman Bill Gates, who said during a keynote on Sunday that Vista has sold more than 100 million copies since its launch in January 2007. That number is impressive, and it surpasses the 89 million copies Windows XP sold during its first year in the market, but that's not that whole picture. InformationWeek explains that the size of the PC market has nearly doubled since XP's launch in 2001. As such, the number of Vista sales was only equivalent to 39% of the number of PCs shipped in 2007-a whopping 255.7 million. XP's 89 million sales, on the other hand, were equivalent to 67% of the 132.4 million PCs shipped in 2002.