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.