TreeViewCheckBox_Code_1

var
  Form1: TForm1;

const
  Checked   = 1;
  UnChecked = 2;
  NotAll    = 3;

implementation

{$R *.dfm}

procedure TForm1.FormShow(Sender: TObject);
var
 i: Integer;
begin
 for i:=0 to TreeView1.Items.Count - 1 do
  begin
    TreeView1.Items.Item[i].StateIndex := UnChecked;
  end;
end;