[cpeterso]

Yes, though I don't have a public source for it. I don't know why Firefox's OS version statistics are not public. Wikipedia says 49% of computers in China run Windows XP: https://en.wikipedia.org/wiki/Windows_XP#Support_lifecycle

Microsoft added its "Genuine Windows" copy protection in XP SP3, so XP SP2 is especially common. (Firefox supports both XP SP3 and SP2.)

[yuhong]

This is a myth actually, and I hope they can kill XP SP2 support in 2015. At least getting rid of the SHA1 cert at the download site at the end of 2015