Microsoft’s claim of 20 million Vista licenses sold simply doesn’t add up when trying to assess who realistically bought them in the time frame—”in the opening month”—stated in today’s press release. Further, the press release claims that “Windows Vista made a splash in its debut.” What kind of Kool-Aid are they drinking up there in Redmond? Who spiked the Windows Vista-logo soda cans?
Stretching the truth is not uncommon in this industry, and Microsoft has become quite good at it. This article points out that Microsoft did just that with regards to their "20 million" Vista sales announcement. It’s a rather long read, but the math is there.
Source: Microsoft-Watch