public class Service : System.Web.Services.WebService
{
    public TicketHeader Ticket;
    public DataSet ds;

    private string machine = "pcName";
    public string userName = "********";
    public string password = "*********";
    public IntPtr token;
    public WindowsImpersonationContext impersonationContext;

    [DllImport(@"D:WindowsSystem32advapi32.dll")]
    public static extern bool LogonUser
    (string lpszUserName, string lpszDomain, string lpszPassword, int dwLogonType, int dwLogonProvider, out int phToken);
    public void Login()
    {
        int returnedToken;
        if (LogonUser(userName, machine, password, 3, 0, out returnedToken))
        {
            token = new IntPtr(returnedToken);
        }

    }

    [WebMethod]
    public DataSet GetDataSet(string id)
    {
        DataSet ds = null;

        Login();
        impersonationContext = WindowsIdentity.Impersonate(token);

        SqlConnection conn = null;
        SqlDataAdapter da = null;
        try
        {
            string sql = "Select * from Table";
            conn = new SqlConnection(@"Data Source=.SQLEXPRESS; Integrated Security=True;" +
                    @"AttachDbFilename=|DataDirectory|ORLDatabase.mdf;");
            conn.Open();
            da = new SqlDataAdapter(sql, conn);
            ds = new DataSet();
            da.Fill(ds, "Table");
        }
        catch (Exception ex)
        {
            throw new Exception(ex.Message);

        }
        finally
        {
            if (conn != null)
                conn.Dispose();
        }

        impersonationContext.Undo();
        return ds;
    }
}