Windows 8 has reached 3.17% market share for desktop operating systems since Microsoft launched the new OS, according to figures from Net Applications.

Windows 8 is now fourth in the pecking order, but the slow progress in the six months since launch is seen as a worrying sign for the PC industry.

Windows 8 is still behind the much maligned and ageing Vista, which fell to 4.99%, and well behind the even older Windows XP (39%) as well as Windows 7 (45%).

Although Windows 8 has already overtaken Apple's OSes, its slow uptake is seen as a concern to the PC industry as it struggles against tablets built for mobile operating systems such as Android and iOS.

Dell, currently in negotiations for a buyout, cited the slow growth of Windows 8 as one reason shareholders should consider a proposed buyout from founder Michael Dell and a consortium of companies, including a $2bn investment from Microsoft.

The plans are still under negotiation, with rival bidders also circling, but a filing with the financial regulator in the US - first spotted by Forbes - highlights concerns over the health of the Windows-based PC industry.

Dell painted a gloomy picture, with "projections for decreased revenue relating to the introduction of the Windows 8 operating system, an unexpected slowdown in Windows 7 upgrades and the growth of tablets and smartphones as alternatives to Dell's core inventory of desktop and laptop PCs".

The company also noted "the increasing usage of alternative PC operating systems to Microsoft Windows, which is incorporated into substantially all of the company’s current PC offerings".