How To Use MSXML2.DOMDocument In ASP?

I need to use MSXML2.DOMDocument in my ASP page. The following is my code:

xml.asp:
=====
<%
dim sx
sx="<root><a>text1</a><b>text2</b></root>"
dim xd
set xd=Server.CreateObject("MSXML2.DOMDocument")
xd.loadXML(sx)
Response.write xd.hasChildNodes
%>

Somehow, xd.hasChildNodes return False, i.e. there is nothing in the xd. I
guess the error was caused by missing the path of the MSXML2 library file. It seems
like the code doesn't know where the MSXML2.DOMDocument is. But the code didn't
generate any error.