The best and easiest way is to make use of the XML DOM (XML Document Object Model) ActiveX object.
Basically, you start with:
code:
var xmldom = new ActiveXObject("Microsoft.XMLDOM");
and then you use anything you like provided by this object. You can load, create, save, modify, browse,... Look around, eventually try to find something about it on Google if you really don't know. There is really nothing you can't do with XML files when using the XML DOM.
(Okay, maybe there is, but that'd have to be a very complex/rare thing you'd want to do.)
Some good references about the XML DOM:
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