PC shipment estimates for the third quarter are out today, and show that the PC market has declined yet again – for the sixth straight quarter. Though shipments saw a slight pick-up due to the back-to-school season, the worldwide PC market is still expected to decline through 2014.

The hope going into last year’s holiday season was that Windows 8 would help drive upgrade sales of PCs. That did not happen, and now PC makers are relying on Microsoft’s Windows 8.1 operating system to pick up the slack. In fact, the plan by Microsoft and its partners is that the coming shutdown of support for Windows XP will force businesses to upgrade their infrastructure in the coming months. The problem for Microsoft, though, seems to be that no one wants Windows 8 (though it did recently become more popular than Vista).

ZDNet this week reported that nearly all of PC manufacturer Toshiba’s sales to business customers include Windows 7 software, rather than Windows 8. Toshiba’s business-to-business product marketing manager is quoted in the report as saying that, “Windows 7 is clearly the enterprise operating system at this time.” She goes on to say that “99 percent” of Toshiba’s business sales are Windows 7 with “few exceptions in corporate America.”

This news comes as a blow to Microsoft, which has seen slow growth of its latest operating system. Toshiba is one of the PC manufacturers that significantly increased its year-over-year PC shipment numbers in the U.S. (up 13.5% to 1.1 million units), much of it from an increase in enterprise sales. If the transition of business from Windows XP lands them on Windows 7, it could be years before those businesses upgrade once again. This, in turn, could make Windows 8 a lost cause that is soon replaced with something more enterprise-friendly from Microsoft.

(Image courtesy Toshiba)