It's not working for me. In the httpd.conf file, the HeaderName line is set to HEADER.html, and I have a file named HEADER.html in the DocumentRoot (which works fine when calling other files). The HEADER.html file just has some simple HTML in it, including the standard starting tags of a file (HTML,HEAD,TITLE,BODY), and the words Testing Header in it. When that didn't work, I just tried taking out all the HTML and leaving Testing Header there, but it still didn't work.
There's no files that match any of the names specified in DirectoryIndex in that folder, I'm not using the file:// thing before my URL; it's using localhost. All the files work fine, and I really have no clue why this isn't working for me...