Microsoft announced today that it has sold more than 40 million licenses for Windows 8 since its launch four weeks ago. That’s double the normal monthly level for Windows 7 over the past three years.

“The journey is just beginning, but I am pleased to announce today that we have sold 40 million Windows 8 licenses so far,” Microsoft Corporate Vice President Tami Reller said during a speech at a Credit Suisse technology conference.

Reller noted that Windows 8 sales are “on pace” with those of Windows 7 at the same period of time after its release. (A Microsoft blog post claims Windows 8 sales are “outpacing” those of Windows 7.) Microsoft didn’t announce Windows 7 license sales after one month, making a direct comparison impossible. But Microsoft did announce that it had sold 60 million Windows 7 licenses in its first two months back in 2009.

I had previously reported that Windows 8 hadn’t met Microsoft’s internal sales projections, and followed up that exclusive with another report detailing the firm’s complaints against PC makers, which it blames for the shortfall. It’s worth nothing that most of the license sales in the 40 million figure were to PC makers, and not to end users. So the actual number of Windows 8 users worldwide is lower than 40 million, though Microsoft didn’t break down the sales between PC makers and individuals.

Microsoft also didn’t reveal how many Surface with Windows RT tablets were sold in the first month. The Surface debuted alongside Windows 8 in late October, and a more powerful version of the device, running Windows 8, is expected in January. The firm currently sells the devices only through its own online and retailer stores, though my sources say that will change in 2013. For more, see "Microsoft: Surface Sales Far From 'Modest'."