I believe non-pirate Windows penetration is quite high atleast on USA/Europe. My logic here is simply that even while a lot of people may be using pirated keys, they probably also have some OEM windows that came with their desk/laptop. For example with a
laptop you may get XP Pro with the HDD in 2 FAT32 partitions. Of course you Could convert it to NTFS but if memory serves me right the default cluster size after that may be on the low side - not absolutely sure though. Anyway small HDD in 2 partitions and
possible non-optimal cluster size. In the laptop case the activation would not have been that big deal but any power user (I think many developers are power users too) could be tempted to re-install with a "non-activation" key. Well in any events I think most
people have Windows but whether they actually use it is a different question.