Microsoft’s free Windows 10 upgrade is clearly going well. Back in October the software giant revealed that 110 million devices were running Windows 10, and that number has now jumped to more than 200 million. Microsoft first released Windows 10 as a free upgrade for Windows 7 and Windows 8.1 users on July 29th, so in less than six months it’s well on its way to reaching 1 billion devices.

Tracking Microsoft’s Windows 10 numbers is important to see whether the company can quickly reach its goal of 1 billion devices within two or three years. The key will be whether Microsoft can maintain this momentum throughout the year. Windows 10 is only supposed to be a free upgrade until July 29th this year, but it would be surprising to see Microsoft start charging for upgrades at all this year.

Microsoft continues to tempt developers to the Windows Store

Windows 10’s install base is also a good indicator of whether Microsoft’s approach to encourage developers to the Windows Store will succeed. Microsoft claims the Windows Store has seen "dramatic growth" during 2015, thanks to an increase in the number of paid transactions. That might help increase developer momentum, but the move to universal Windows apps has been slow so far, despite some promising interest from big names.

Alongside the numbers, Microsoft is also expanding its Surface Book availability. Preorders will begin tomorrow in Austria, Australia, France, Germany, Switzerland, New Zealand, and the UK. The Surface Book roll out will start initially in Australia and New Zealand on January 28th, followed by the rest of the new markets on February 18th. Microsoft is also bringing the Surface Book to China and Hong Kong on January 15th, and "soon" to Japan.