Tami Reller, corporate vice president (and chief financial officer and chief marketing officer) for Windows and Windows Live, announced today that Microsoft has sold 40 million Windows 8 licenses after its first month of retail availability.

Is that number good, bad, or merely mediocre? Probably good, but perhaps not great. Microsoft sold 60 million copies of Windows 7 in the first ten weeks of that operating system's availability, with the Wall Street Journal estimating that 40 million copies were sold in the first month.

With Windows 8 selling 40 million copies in five weeks, it seems to be selling at about the same pace as Windows 7. Considering the different market dynamics—Windows 7 was an iterative release that fulfilled substantial pent-up demand as businesses chose to ignore Windows Vista whereas Windows 8 is a more controversial update being brought to a market that is generally happy with Windows 7 anyway—this is a healthy performance. Windows 7 sold very well and matching it is no mean feat. The apparent failure to surpass Windows 7's launch could explain the mixed reports on early sales. Strong sales can still be disappointing if they were expected to be stronger still.

There are a few provisos, however. First, there's the usual hand-waving that comes when companies report sales figures; there's a difference between copies sold to retailers and OEMs, and copies sold to end-users. The former number is always higher than the latter, with the difference representing stock sitting in warehouses and on store shelves. The latter number, however, is the one that indicates the level of interest and acceptance by actual users, and it's also the one that indicates the size of the market for Windows 8-specific Windows Store applications. This complaint isn't unique to the Windows 8 numbers; the same is true of the Windows 7 reports too.

Second, Reller noted that the number of upgrades to Windows 8 was outpacing the volume of upgrades to Windows 7 in the equivalent timeframe. What she didn't note was that Windows 8 upgrades are substantially cheaper than Windows 7 upgrades were, as Microsoft is selling upgrades for $39.99 in a time-limited offer that runs to the end of January 2013. This offer is likely to be stimulating sales of the upgrade licenses but might not necessarily be translating into Windows 8 installations, with some users buying the license now but sticking with Windows 7 as a hedge against price rises in future.

Reller offered some other numbers to suggest that consumers were getting along with Windows 8 better than some expected: 90 percent of users manage to use the charms on their first day, 50 percent visit the Windows Store on the first day, and 85 percent launch the desktop on the first day. Several apps have already enjoyed 1 million downloads, and several more are close to that. One thing she didn't provide was a number of Surface sales. We still have no data on how well Microsoft's first foray into the PC hardware market is doing.

Even with these provisos, it's clear that Windows 8's launch is far from a failure and that the PC market isn't dead yet. Apple sold about 40 million iPads in the whole of 2011 and OS X has about 66 million users total. The PC market may not have exploded the way some OEMs and retailers might have hoped, but it certainly hasn't collapsed just yet.