export data from gridview to msword

Question

HI 
  Frnd's.., I had try below showing code to convert data from gridview to msword..but the end data is saved in notepad  i need to save in msword..can any1 help..

protected void btn_export_Click(object sender, EventArgs e)

{

GridView1.AllowPaging = false;

        GridView1.DataBind();

        Response.ClearContent();

        Response.AddHeader("content-disposition", string.Format("attachment;filename{0}", "customer.doc"));

        

         Response.Charset = "";

        Response.ContentType = "application/ms-word";

        StringWriter sw = new StringWriter();

        HtmlTextWriter htw = new HtmlTextWriter(sw);

        GridView1.RenderControl(htw);

        Response.Write(sw.ToString());

        Response.End();

        lab_msg.Text = "data saved";

        lab_msg.ForeColor = Color.Green;

    }

                        thank you..