Code:

unit Unit4;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, ComCtrls, ShellCtrls, WinSkinData;

type
  TForm4 = class(TForm)
    SkinData1: TSkinData;
    ShellComboBox1: TShellComboBox;
    ShellTreeView1: TShellTreeView;
    Button1: TButton;
    ShellListView1: TShellListView;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    procedure SetBottomWindow;
    procedure WMNCPaint(var Msg: TWMNCPaint); message WM_NCPAINT;
  end;

var
  Form4: TForm4;

implementation

{$R *.dfm}

procedure TForm4.SetBottomWindow;
begin
  SetWindowPos( Handle, HWND_TOPMOST,
                Left, Top, Width, Height,
                SWP_NOACTIVATE or SWP_NOMOVE or SWP_NOSIZE or SWP_NOOWNERZORDER);
end;

procedure TForm4.WMNCPaint(var Msg: TWMNCPaint);
begin
  SetBottomWindow;
  inherited;
end;