Microsoft is experiencing an unexpected surge in its stock price this week after a decade and a half of stagnation. But don’t look to the recently released Windows 8 as the catalyst for this change: According to the latest usage share statistics, Windows 8 is barely moving the needle.

Microsoft’s stock price hit $33.10 at the close of business on Tuesday, its highest point in over five and a half years: In mid-December 2007, Microsoft was trading at over $36 briefly, but the stock has been stuck in the mid-$20s ever since. Indeed, if you factor out a strange upsurge in late 2007, Microsoft’s stock has been stuck at that level for over a decade.

Speculation abounds as to the cause of the upsurge. But Microsoft, long seen as a slow-growth company with aging software businesses, recently surprised investors with spectacular quarterly earnings that belie the troubles in the PC industry. It seems that investors are finally figuring out that the firm is doing a spectacular job transitioning from its traditional businesses to a new world of online services. This year, it will have created at least two new billion-dollar businesses, Azure and Office 365, both of which are entirely cloud-based. (Azure just crossed that line, actually.)

Although Windows remains one of Microsoft’s biggest businesses, we can’t give the latest version, Windows 8, any credit for this remarkable (and potentially temporary) financial turnaround. The firm has suspiciously declined to provide an updated Windows 8 license sales figure in recent months, but usage data suggests that the OS is off to a slow start. How slow? How about “slower than WIndows Vista” slow?

NetApplications, which measures desktop OS usage share, reported this week that Windows 8 now accounts for just 3.8 percent of worldwide OS usage in April 2012, up barely from the 3.3 percent figure a month earlier. That usage trails Windows 7 (45 percent usage) and Windows XP (38.3 percent) by a wide margin, of course. But it even trails the derided Vista, which somehow still accounts for 4.75 percent of OS usage.

Worse, usage of Windows 7 isn’t falling as Windows 8 rolls on: Month-over-month usage in Windows 7 was essentially flat. And although XP usage did decline somewhat, it’s worth pointing out that XP usage is fully 10 times that of Windows 8. Not bad for a 12-year old OS.

In the good news department, Windows 8 is in use by more people than is the most-often-used version of Mac OS X, version 10.8, which obtained just 2.8 percent usage share in the month. And Windows overall continues to dominate the competition with 92 percent usage share, compared with 7 percent for Mac OS X and 1.2 percent for Linux. That’s another consistent trend from the past decade.