public partial class Form1 : Form
    {

        [DllImport("User32.dll", EntryPoint = "FindWindow")]
        private static extern IntPtr FindWindow(string lpClassName, string lpWindowName);
        [DllImport("user32.dll")]
        public static extern bool ClientToScreen(int hwnd, ref POINT pos);

        [StructLayout(LayoutKind.Sequential)]
        public struct POINT
        {
            public int X;
            public int Y;

            public override string ToString()
            {
                return "{" + X + "," + Y + "}";
            }
        }

        public Form1()
        {
            InitializeComponent();
        }

        bool isWork = true;
        private void button1_Click(object sender, EventArgs e)
        {
            new Thread(() =>
            {
                while (isWork)
                {
                    var handle = FindWindow(null, "QQ");
                    if (handle == IntPtr.Zero) break;
                    POINT p = new POINT();
                    if (ClientToScreen(handle.ToInt32(), ref p))
                    {
                        this.Invoke(new Action(() =>
                        {
                            Location = new Point(p.X, p.Y - Height);
                        }));
                    }
                    Thread.Sleep(100);
                }
            }).Start();
        }

        private void button2_Click(object sender, EventArgs e)
        {
            isWork = false;
        }