Microsoft is pretty happy about how Windows 8 is doing, but 40 million license sales isn't exactly translating to a boon for the PC market. According to NPD, sales of Windows-powered devices are 21 percent lower than they were during the same time period last year -- October 21 through November 17. Of course, Windows 8 didn't actually hit shelves until the 26th, which may have skewed the numbers a bit as consumers held out for the latest and greatest from Redmond. The weakness of the desktop and laptop market are partially to blame, but while license sales for Windows 8 are outpacing its predecessor, there is some cause for concern. Specifically that, after a few weeks, the touch friendly revamp of the OS is only shipping on about 58 percent of new machines. Four weeks after the launch of Windows 7, it was preloaded on 83 percent of new hardware. Worse yet, according to the NPD, tablet sales "have been almost non-existent." Of course, things could pick up as we enter the holiday season, but it's not entirely clear that Windows 8 will be able to lift the sagging PC market on its back. The full PR awaits you after the break.