According to The Register, the "Taiwanese Consumer Foundation...claims [Microsoft] is effectively using its monopoly to force sales of Vista."
How? Well, as the TCF reasons, since most buyers would prefer XP, as demonstrated by their installing XP even after buying a Vista-enabled computer, forcing them to buy Vista in the first place is tantamount to an exercise of monopoly power.
The problem with such reasoning is that the same could be said of any software vendor (perhaps minus the monopoly power). Microsoft already supports its products for a very long time, and expecting customers at some point to move to the latest and greatest (and more cost effectively supported) is not a bad policy. Any vendor should be hoping the TCF loses on this one.
Microsoft, for its part, had better pray Windows 7 comes without the complaints that Vista has delivered. Two bad product releases in a row? Even Microsoft may not be able to survive that.