IE7 will support a scriptable native version of XMLHTTP
XMLHTTP was first introduced to the world as an ActiveX control in Internet Explorer 5.0. Over time, this object has been implemented by other browsing platforms, and is the cornerstone of “AJAX” web applications. The object allows web pages to send and receive XML (or other data) via the HTTP protocol. XMLHTTP makes it possible to create responsive web applications that do not require redownloading the entire page to display new data. Popular examples of AJAX applications include the Beta version of Windows Live Local, Microsoft Outlook Web Access, and Google’s GMail.
http://blogs.msdn.com/ie/archive/2006/01/23/516393.aspx
