If you're using an operating system that's over a decade old to play Blizzard games, we have some bad news for you. Starting in October, Blizzard says it will "begin the process of ending support for Windows XP and Windows Vista in World of Warcraft, StarCraft II, Diablo III, Hearthstone, and Heroes of the Storm."

The fact that Blizzard was still supporting these long-in-the-tooth Microsoft OSes (XP launched in 2001, Vista launched in early 2007) says something about the long tail of low-end hardware that the company targets alongside top-of-the-line modern systems. Though Microsoft dropped mainstream support for Windows XP and Windows Vista years ago—and ceased issuing security fixes for the operating systems in 2014 (with another issued earlier this year )—Blizzard says that a "decent portion of our audience was still using" the platforms long after Microsoft left them for dead. Three major Windows releases later, though, the "vast majority of our audience has upgraded" to a more recent OS, Blizzard says.

Windows XP's longevity was something of an outlier in the world of PC operating systems, still seeing significant adoption a decade after its launch . When Microsoft finally pulled the plug on mainstream support for the OS in 2014, it was still running on 29 percent of Web users' PCs . Even today, XP commands a surprising 6.4 percent of all desktop Web users, according to NetMarketShare, far ahead of Vista's 0.53 percent.

Blizzard's move will probably have the biggest practical effect in countries with developing economies, where old computers that can only run older operating systems still have some popularity in budget gaming cafes. Even in the developed world, though, you can still find online guides to building budget gaming rigs based on XP.

Earlier this year, Microsoft told its corporate partners to start migrating away from Windows 7, which will at least receive security updates through 2020.