Microsoft earns most of its keep selling software licenses to OEMs, who bundle Windows with a new PC, any PC. So, yes, I suppose it’s possible that Microsoft has booked 100 million sales into its ledgers. But that doesn’t mean that 100 million copies of Windows 8, or anything close to that number, are in the hands of end users. It may also be true that there are tens of millions of unsold PCs in the channel. But that doesn’t matter to Microsoft, since a sale is a sale even if nobody is actually using the product.
That puts a whole different spin on things.