According to data from research firm IDC, PC sales fell 6.4pc between October and December – far worse than had been expected.
"Although the third quarter was focused on the clearing of Windows 7 inventory, preliminary research indicates the clearance did not significantly boost the uptake of Windows 8 systems in Q4," said Jay Chou, a senior research analyst at IDC.
In the US, PC sales slid 4.5pc in the final three months of 2012, and 7pc for the full year.
That has led to what many see as an inexorable decline in the PC market, but IDC laid at least part of the blame on Microsoft for failing to market Windows 8 properly.
"Consumers expected all sorts of cool PCs with tablet- and touch-optimised capabilities," said IDC's David Daoud.
"Instead, they mostly saw traditional PCs that feature a new operating system (OS) optimised for touch and tablet with applications and hardware that are not yet able to fully utilise these capabilities," he added.
Even though Mr Daoud referred to Windows 8 as "traditional", the changes in the OS, such as the removal of the long held "start" button on the desktop, caused consternation among some consumers who either switched to Apple or stuck with their older machines running Windows 7 or even the 12-year-old Windows XP.
News of falling PC sales came as Apple's chief executive, Tim Cook, said he expected the Chinese market to eventually overtake the US as his company's biggest market.
" China is currently our second largest market. I believe it will become our first. I believe strongly that it will," Mr Cook told Chinese state media.
Apple posted sales in China of $5.7bn (€4.3bn) during its most recent quarter, about 16pc of the company's total revenue.