Source -The latest iteration of the Windows client has long passed the 100-million-sold-license milestone, and the fastest selling operating system in history doesn’t show any signs of stopping. Furthermore, Windows 7’s main victim, in terms of OS market share, is the nearly-decade-old Windows XP. Statistics provided by Internet metrics company Net Applications reveal that both XP and Windows Vista users are converting en masse to Windows 7, month after month, fueling its growth.
In just the first six months after General Availability, Windows 7’s slice of the market exploded to a share of over 10%. At the end of April 2010, the successor of Vista accounted for no less than 11.68% of the operating-system market, up from 10.23% the previous month. The correlation between Net Applications’ OS usage data and the actual sales of the platform indicates that Microsoft has already sold approximately 120 million copies of Windows 7.
Windows 7 Grows Feeding Off XP - And Vista, but to a lesser degree - Softpedia