[marcoszorrilla]

Comprobado que este código que te adjunto funciona:

Código Delphi [-]
unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,ComObj,
  StdCtrls;

type
  TForm1 = class(TForm)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.DFM}

procedure TForm1.Button1Click(Sender: TObject);
var
  excel:Variant;
  hoja:OleVariant;
  libro:OleVariant;

begin
  try
    excel:=CreateOleObject('Excel.Application');
  except
    ShowMessage('Excel no se pudo iniciar.');
    exit;
  end;
  excel.Visible:=true;
  excel.Workbooks.Add;

  Libro := Excel.WorkBooks.Add;
  Hoja := Libro.ActiveSheet;
  Hoja.Cells[1, 1] := 'Hola mundo';

  Libro.SaveAs('ejemplo.xls');
  Excel.Quit;

end;

end.

Un Saludo.