Digitimes has another reason for Windows 7 sales to be low.
PC replacement demand is not driven significantly by the consumer market, but rather enterprise and government purchases
... most enterprises in Europe and North America are expected to start planning annual purchasing budgets for the year in March and April of 2010, actual replacement demand is not expected to spur until the second half of the year.
Companies and government might buy computers next year, but they should already be buying orders placed in March and April of this year. There are already accounts of corporate rejection of Windows 7, so that OS is not likely to have anything to do with corporate buying and government won't be a big market because UAC still does not meet government security standards . Back in January, retailers at CES remembered being "burnt by Vista" and saw nothing to change their minds about the contracting PC market. Perhaps OEMs and retailers could deliver the gnu/linux netbooks and desktops that people actually want to buy.