Use TreeView_SelectItem for the drop source and TreeView_SelectDropTarget
for the drop target. You may also want the "track select" style turned on
and use TreeView_CreateDragImage for the source item.

Use TreeView_GetItem, then TreeView_DeleteItem and TreeView_InsertItem to
move it. (Using TreeView_GetItem with all the flags set should get you as
much information as you need to re-insert the item without losing
information.)

This still won't quite be like the menus (it will select an item rather than
show an insertion point between items) but it's probably as near as you are
going to get with a tree.

See "CTreeCtrl, drag and drop operations" in MSDN for more information.