According to Petri.com, Windows 10 is off to a pretty fast start. Apparently, although it's only been officially available for just under two months, Windows 10 has been installed on over 100 million machines--meaning that it's well on its way toward Microsoft's goal of one billion machines within three years.
Clearly, if Microsoft is going to compete against iOS and Android, which run on over a billion machines collectively, Windows 10 must become the PC operating system of choice. The Universal apps strategy depends on it, certainly, and thus Windows 10 Mobile. Microsoft' mobile platform has historically suffered from a dearth of apps compared to the competition, and Universal app support on Windows 10 Mobile requires a large Windows 10 installed base across all machine types in order to hold any chance for success. Everything else depends on the same kind of ubiquity as well, from Cortana to OneDrive to a generally strong Windows 10 OEM ecosystem.
Windows 7 remains the most popular Windows version by far, but 100 million Windows 10 installations is nothing to sneeze at. The impending release of Windows 10 Mobile and new flagship hardware, including the Surface 4 and new high-end Windows 10 Mobile handsets in the Lumia 950 and 950XL, should also help increase these numbers.
Long-term, getting to a billion Windows 10 machines will likely depend on enterprise upgrade cycles. In the short-term, however, it's great to see Windows 10 at least grabbing the low-hanging fruit.Further reading: Windows 10