Unsurprisingly, IE9 won't be supported on an obsolete OS
Internet Explorer General Manager Dean Hachamovitch all but confirmed today that the next version of Microsoft's Web browser, Internet Explorer 9, will not be supported on Windows XP.
Hachamovitch stopped short of explicitly saying that XP would not be supported, but said that building a "modern browser" required a "modern operating system." IE9 will be heavily dependent on hardware acceleration, courtesy of its use of Direct2D and DirectWrite; neither API is available on Windows XP.
Read it here.