int i = 60;
    private void timer1_Tick(object sender, EventArgs e)
    {

        if (i == 0)
        {
            timer1.Stop();
            label1.Text = "";
        }
        else i--;
    }

    private void button1_Click(object sender, EventArgs e)
    {
        timer1.Interval = 1000;
        timer1.Start();
    }