Is Internet Explorer 9 compatible with Windows XP?
No: http://windows.microsoft.com/en-gb/internet-explorer/downloads/ie
What you're looking at specifically is the phrase 'Available for Windows 7 and Windows Vista.'
The answer is no because Internet Explorer 9 uses Direct2D for hardware acceleration which is incompatible with Windows XP. Internet Explorer 9 is designed for Windows Vista, Windows 7 and Windows 8 only.