public Form1()
    {
        InitializeComponent();
        Thread usage = new Thread(new ThreadStart(Usage));
        usage.Start();

    }
    public void Usage()
    {
        PerformanceCounter CpuCounter;
        CpuCounter = new PerformanceCounter();
        CpuCounter.CategoryName = "Processor";
        CpuCounter.CounterName = "% Processor Time";
        CpuCounter.InstanceName = "_Total";
        while (true)
        {
            label3.Text = String.Format("{0}", CpuCounter.NextValue());
            Thread.Sleep(100);
        }
    }