Microsoft has confirmed that it has sold 40 million Windows 8 licences since launching the operating system in October.

“The journey is just beginning, but I am pleased to announce today that we have sold 40 million Windows 8 licenses so far,” Tami Reller, the chief marketing and financial officer for Windows, told the Credit Suisse 2012 Annual Technology Conference.

Those numbers mean that Windows 8 is outpacing Windows 7 in terms of upgrades - no mean feat considering the desire by many to leave Vista behind as quickly as possible.

READ: Windows 8 review

It's the second big number surrounding Windows 8 that Microsoft has been keen to tell us about. Four days after the launch of the operating system on 26 October, Microsoft revealed that four million customers had paid for a Windows 8 upgrade.

“The level of embrace from enthusiasts, from people who want to get out there, is very, very high,” said Ballmer at the time.  

Despite Microsoft’s impressive sales figures, it is worth noting that the company is actually offering the upgrade at a more affordable price point than when Windows 7 was introduced.