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.

Both Vista and Windows XP lost market share the previous few months, a trend that gained more consistency as Windows 7 hit store shelves. Vista dropped from 16.01% to 15.60% between March and April 2010, and down from 18.83% in October 2009, when its successor was launched.

Windows XP’s market-share drop has been more steep, both in the past couple of months, and over the past half a year. XP is currently accounting for just 63.41% of the OS market, while it owned 64.46% in March 2010 and 70.48% in October 2009. Between October 2009 and April 2010, Windows 7 jumped from 2.15% to 11.68%, an increase that obviously came to the detriment of its predecessors.

“The most important product our company has launched in the last year, no doubt, was Windows 7. Windows is a very important piece of infrastructure on literally over 1 billion PCs around the planet, and then the server version of Windows is also very important, running on over 7 million servers around the world,” Steve Ballmer, CEO of Microsoft, revealed at the IDC Conference in Brazil on April 28, 2010.

Microsoft Windows 7 90-Day Eval VHD is available for download here.
Another Windows 7 RTM Enterprise 90-Day Evaluation is available for download here.