---

private void label1_MouseHover(object sender, EventArgs e)
{
    label1.TextAlign = ContentAlignment.MiddleCenter;
    label1.Text = "ERROR!!!";
    label1.ForeColor = Color.Red;
    MessageBox.Show("Написано же\nНЕтрогать!", "Fatal ERROR!", 
        MessageBoxButtons.OK, MessageBoxIcon.Error);
}




private void Form1_Load(object sender, EventArgs e)
{
    this.Text = "Hover";
    label1.TextAlign = ContentAlignment.MiddleCenter;
    label1.Text = "Не трогай.";
}