OK - I've got this one....:-)

I just did that very same thing in my skin at http://demo.martinmoesby.com.

1st you have to add 2 solpartmenu controls to your skin.

The first control should have the RootOnly="true" attribute, the second control should have the level="child" attribute. Furthermore you could try the ForceDownLevel and ForceFullMenu attributes.

One major issue in this approach is that you cant get the to Admin menu without adding a bit of script in your Skins Page_Load() event..

I've solved this by adding this code to my skin :

<script runat="server">

    Sub Page_OnLoad(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

        If dnnMenu.AdminMode Then dnnMenu.RootOnly = False

    End Sub

</script>