Analyst firms IDC and Gartner have published figures that show shipments of personal computers dropped much more than expected in the first quarter of this year.
The total number of PCs shipped worldwide was 76.3 million units, IDC said, a decline of 13.9 percent compared to the same period last year.
Fellow analyst firm Gartner pegged worldwide PC shipments for the quarter at 79.2 million units, an 11.2 percent freefall from the first quarter of 2012.
IDC had forecast a drop of 7.7 percent and the decline is the steepest ever for a single quarter. Gartner noted it was the first time since 2Q09 that unit shipments fell below 80 million.
Microsoft's new Windows 8 operating system is largely to blame for the weak sales, IDC believes.
"At this point, unfortunately, it seems clear that the Windows 8 launch not only failed to provide a positive boost to the PC market, but appears to have slowed the market," said IDC analyst Bob O'Donnell.
"While some consumers appreciate the new form factors and touch capabilities of Windows 8, the radical changes to the UI, removal of the familiar Start button, and the costs associated with touch have made PCs a less attractive alternative to dedicated tablets and other competitive devices".
IDC said Microsoft will need to "make some tough decisions" to kickstart the PC market and help the industry to innovate and differentiate.
HP is still the world's largest PC vendor with a 28.5 percent market share, followed by Lenovo, Dell, Acer and ASUS.
Of the five, only Lenovo managed to keep it sales steady, whereas Acer saw an almost third drop and HP nearly a quarter.