Microsoft has announced that Windows 7 has sold more than 300 million licenses so far, meaning it is still the fastest-selling operating system. Windows 7 has been available to the masses for 15 months.

"To put that in perspective, 300 million is roughly the combined number of households in North American and in Europe," a Microsoft spokesperson said in a statement. "Or, to put it another way, if you lined up 300 million Windows 7 product boxes, they would stretch nearly 1.5 times around the Earth! As of today, over 20% of Internet-connected PCs worldwide are running Windows 7 according to Net Applications."

Windows 7 actually grabbed 20 percent of the market at the end of 2010. Between January and December 2010, Windows XP fell almost 10 percentage points to 56.72 percent market share, Windows Vista lost over five percentage points to 12.11 percent, and Windows 7 gained over 13 percentage points, pushing it to 20.87 percent.

Three months after release, Microsoft said more than 60 million Windows 7 licenses were sold. Doing some simple math, it appears that sales still haven't slowed down.

If you're already on Windows 7, you should check out our guides for Microsoft's latest operating system. If you haven't upgraded to it yet, tell us why in the comments below.