start Windows service แล้ว service ไม่ทำงาน ช่วยดูให้หน่อยครับว่าผิดตรงไหน

public MainForm()
{
        InitializeComponent();
        WriteLog("Process Started");
}

private void WriteLog(string text)
        {
            StreamWriter sw = new StreamWriter(Environment.GetFolderPath(Environment.SpecialFolder.Desktop) + @"\test.txt", true);
            sw.WriteLine(DateTime.Now.ToString() + " : " + text + "\n");
            sw.Close();
        }

protected override void OnStart(string[] args)
        {
            WriteLog("Process Started");
            base.OnStart(args);
        }