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type
  TForm1 = class(TForm)
  protected
    procedure WMNCHitTest(var Message: TWMNCHitTest); message WM_NCHITTEST;


implementation

procedure TForm1.WMNCHitTest(var Message: TWMNCHitTest);
begin
  inherited;

  if Message.Result = HTCLIENT then
    Message.Result := HTCAPTION;
end;					

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procedure TForm1.Image1MouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
const
  SC_DRAGMOVE = $F012;
begin
  if Button = mbLeft then
  begin
    ReleaseCapture;
    Perform(WM_SYSCOMMAND, SC_DRAGMOVE, 0);
  end;
end;