I think I need to clarify a few things. 

1)  The default dnn install already comes with the dnntree webcontrol.  Downloading and installing the zip is not necessary, whatever zip that may be, unless you require the file to be updated with the latest version (which is still in beta)

2)  There is a difference between a webcontrol and a dnn module.  A webcontrol is something a developer uses to create functionality (i.e. grid, menu, etc.)  A webcontrol in and of itself does not provide functionality, it typically allows a developer to offer some sort of UI.

3)  There are already a few things inside dnn that utilize the dnntree.  For example, if you change your skin to the vertical blue, you will see the menu webcontrol replaced with the tree webcontrol.  Additionally, some of the admin modules use the tree like the resource manager and file manager.

So, the question you need to ask yourself is what exactly do you want the tree to do?  Show files, show navigation, or something completely custom?   If it is something custom, I do offer a video for free with source code showing an advanced module developed with the treeview control at http://www.codeendeavors.com/Downloads.aspx. 

Hope this helps.

jgurley wrote I did know that the File Manager, for example, uses it, but it never occurred to me (duh) that that meant it was already installed.  As I was saying... All I want to do is produce a nested list of links to local files, opening a file in another pane. I know how to do it in non-DNN javascript, but am not sure out to use dnntree.  I looked at your demo and it didn't turn any lights on... 2008     Jan        file1        file 2     Feb        file 3        file 4 2007     Jan        file 37   etc.

It sounds like what you want to use the tree for would require a custom module.   It doesn't sound too in-depth, and if you have done similar in Javascript, once you have the tree in a module...it's fairly easy to work with.