Only simple way I can think of doing it, would be to have the help files as html, and have the content editable. For example Have the help.html pull it's content from an editable txt file. Users can edit the txt file, thus editing the help file contents.
Although I have Visual studio Pro 2005, I've never really gone in to it in detail. But I know people who use it quite a bit. I'll ask around and see if they have any ideas