>I store some of my application settings in XML files. I was wondering if there is a free (publicly available) XML editor that I can recommend to my customers to use to edit the XMLs? I am thinking of an editor that won't allow user to change (or at least won't make it easy) the XML tags but only the values.

Well, I don't know how hard it would make things, but you might take a look at PXE

With the restriction you want, you might have to write your own.