you can't say for certain the 22% comes from Windows 7, the summer months and leasing in the Fall is also back to school and there also countless sales/deals going on as Intel also released new chips/chipsets so there was plenty of inventory clearing going on. and people buying the latest and greatest hardware, also the margin for PC is also lower since there is more competition, people actually have choices when buying a PC, for a Mac there is only 1 place to go, the competition drives down the profit, but don't be mistaken into thinking they aren't making money or have market share
also most early adopters of the OS are going to be the enthusiasts who will be just buying the parts they need, and not necessarily who PCs