This is all you need to do... :)
1 2 procedure TForm1.TreeView1DragOver(Sender, Source: TObject; X, Y: Integer;
3 State: TDragState; var Accept: Boolean);
4 var5 tn: TTreeNode;
6 begin7 tn := TreeView1.GetNodeAt(X, Y);
8 if Assigned(tn) then9 Memo1.Lines.Add(tn.Text);
10 end;