"Feature creep" is a problem familiar to corporate developers. It describes what happens to applications that never get finished because their feature set is a moving target. But Windows Vista is apparently being hit by a different kind of feature creep: Its performance is being slowed down by some of its features. And not the ones anybody seems to care much about at that.

The Inquirer is reporting that Microsoft is telling game developers that Vista will run their products 10% to 15% slower than XP. The reason is that the Vista desktop uses DirectX.

DirectX is a set of graphics and sound application programming interfaces that let developers address video and sound devices in a PC in a standard way. Ironically, Microsoft originally put DirectX into Windows to entice game developers to port their programs to Microsoft's OS.

But with Vista, Microsoft's own developers have relied on DirectX--and more particularly its 3-D graphics capability--for the fancy Aero interface. It's DirectX that gives Vista that blurred, semi-transparent border around windows. (It's also DirectX that's one of the reasons many existing PCs won't run Vista: Vista requires DirectX 9, and most PCs need an upgrade. Fortunately, it's not a showstopper--you can download it from here.)

Microsoft thinks the Aero desktop is so important that it won't let it be turned off--at least that's what it's telling developers. (I certainly can't find a setting in Vista that will let me downgrade the interface to something less resource-intensive, like the "Windows Classic" look with plain gray borders, even though I might want to.)

As far as I'm concerned, I care about DirectX perhaps even less than I care about games, but I'll bet there's going to be screaming from the gaming community over this--and that's one more community heard from as Microsoft marches toward alienating as many customers as possible with Vista.