Dear wp,
I'm sorry to inform you that it didn't work. When I drag something onto the ShellTreeView the mouse cursor changes to a "forbidden".
I tried to put a normal TreeView on the same form, and even without items in it the DragOver handler is called, and the cursor changes to an arrow+rectangle (correct behaviour). If, in the same TreeView, I delete the OnDragOver assignment, it correctly reverts back to not accepting drags.
Looking better at the hierarchy, it seems that OnDragOver is first declared in TTreeView, not TCustomTreeView which is the common ancestor.
I suppose I will have to use a normal TreeView and populate it by code. It should be not too difficult... unless someone else has some better idea!
Regards,
linuxfan