Error when importing data from Excel: External table is not in the expected format

sir i am following mudassar sir article in aspsnippets to upload excel file ,it is working fine for 2007 format of excel but displaying error "External table is not in the expected format." for 2003 format 

  <add name = "Excel03ConString" connectionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source={0};Extended Properties='Excel 8.0;HDR=YES'"/>
  <add name= "Excel07+ConString" connectionString = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source={0};Extended Properties='Excel 12.0;HDR=YES'"/>

 string extension = Path.GetExtension(FileUpload1.PostedFile.FileName);
        string conString = string.Empty;
        switch (extension)
        {
            case ".xls":
                conString = ConfigurationManager.ConnectionStrings["Excel03ConString"].ConnectionString;
                break;
            case ".xlsx":
                conString = ConfigurationManager.ConnectionStrings["Excel07+ConString"].ConnectionString;
                break;
}
        conString = string.Format(conString, path);
        using (OleDbConnection con = new OleDbConnection(conString))
         {
             con.Open();
          
             string sheet = con.GetOleDbSchemaTable(OleDbSchemaGuid.Tables, null).Rows[0]["TABLE_NAME"].ToString();
             string query = "Select * from[" + sheet + "]";