Does anyone know how these figures are collated as Windows sales might include PCs running Linux, some people build machines and then pirate Windows and web site statistics are open to a whole slew of problems from selection bias through to easy OS spoofing.

I've not heard of an accurate way to produce these statistics yet cnet are displaying floating points as their percentages and publishing them as fact. So I'd hope they have a reasonably accurate method of collation which I'm unaware of.