It's been a great 18 months for Microsoft's Windows 7 as the operating system has managed to sell over 350 million licenses and grab (according to StatCounter) just over 30% of the global OS market, placing second to the immortal that is Windows XP (~ 47% market share).
It may not have the OS crown yet but Windows 7 has surpassed Windows XP in the US, and it can only go further as more consumers and businesses adopt it.
Of course, this winning streak isn't going to last forever and it won't since in 2012 Microsoft is supposed to release Windows 8, an OS that supports both x86 and ARM-based chips, meaning it will work on regular PCs as well as on tablets powered by Tegra/Qualcomm/TI/Samsung chips.

Source :