Since all of the browsers on Windows XP use the Windows SChannel API none of them support SNI. That includes the beloved Google Chrome, FireFox, and Safari. (Not sure about Opera on Windows XP)
That is unfortunately an issue that only Microsoft can rectify unless developers on the Windows platform want to take the time and effort to re-implement parts of the SChannel API.
My apologies regarding FireFox. I don't use FireFox and when I do it is from a Mac OS X machine.
Either way Internet Explorer doesn't support it and as such it is still a no-go from a usability stand point since XP still has such a large market share.
