The evidence looks pretty damning, as you can see from these two screenshots of different Microsoft sites. The first is its main US site and the second is its Polish site:
Screenshots taken from Microsoft's English site and Microsoft's Polish site. As you can see from the full versions on those sites, the person's hand is the same in both and it is the first (US) one that looks to be the genuine photo.
Hat-tip: Engadget
UPDATE: Microsoft have now apologised: "We apologize and are in the process of pulling down the image"
UPDATE 2: Here's the story from the BBC.
A computer thinks the following may also be of interest:
Microsoft should be ashamed of themselves! Thank you for tweeting this!
Not anymore it seems.
They've been rumbled! I am ashamed!