The struggling PC market is taking its toll on both Microsoft (MSFT 1.82%) and Hewlett-Packard (HPQ -0.46%), among others. Windows 8 has been pegged as a major factor contributing to the 14% decline in worldwide PC units in the first quarter, as consumers remain largely confused about the new interface.

Microsoft's upcoming Windows 8.1 upgrade hopes to address some of these criticisms, in part by bringing back a Start Button that launches a Start Screen overlay on top of the desktop, which the company hopes will be "less jarring" than the current implementation where users feel like they're "transported into this whole other world."

Even after considering these improvements, HP is actually more excited about something else entirely: the death of Windows XP. Microsoft announced early last year that it was starting a two-year countdown to ending support for both Windows XP and Office 2003. April 8, 2014 is now less than a year away, after which point Windows XP will no longer receive critical security updates, bug fixes, and other types of support.

Naturally, the solution is to upgrade to either Windows 7 or Windows 8. Microsoft is hoping that enterprise customers, who have a lot more to lose from security threats, will upgrade, noting that the average enterprise deployment can take 18 to 32 months to fully deploy.

That's potentially a big opportunity for vendors like HP, who remains the No. 1 PC seller in the world by volume, although Lenovo is nipping at HP's heels. At a recent press conference, HP displayed a presentation slide titled, "Goodbye XP, Hello HP."

HP PC exec Enrique Lore said he believes that Windows XP's death will be a "big opportunity for HP," triggering a massive enterprise upgrade cycle. Lore also expressed a belief that ending Windows XP support will do "significantly more" to help the PC market than Windows 8.

That optimism is contributing to CEO Meg Whitman's comments today that HP could potentially put up revenue growth next fiscal year, helping keep HP in the green on a broadly down day.

HP may be growing sick of Wintel, but it's still banking on Windows in one way or another.