Windows XP fell below 30% market share in December as Windows 8.x ended the year on a high, crossing the 10% barrier.
Data collected by Net Applications shows that Microsoft's XP operating system fell in usage by 2.24% to end 2013 at 28.98% market share, while 8 and 8.1 enter the New Year with 6.89% and 3.60% market share respectively.
Despite Microsoft ending support for XP in April, a Spiceworks study suggests that 76% of IT professionals are still running the OS 12 years after it was first released.
The latest figures suggest users are beginning to make the switch to 8.x, with 8.1 gaining 0.96% market share during December thanks to a free upgrade option, though 8 recorded just 0.23% growth.
Microsoft is expected to appoint a new CEO early this year, after the resignation of Steve Ballmer last year. He will remain in charge until the new boss takes on the role.