Bit more detail:
private void Form1_Load(object sender, EventArgs e)
{
Timer MyTimer = new Timer();
MyTimer.Interval = (45 * 60 * 1000); // 45 mins
MyTimer.Tick += new EventHandler(MyTimer_Tick);
MyTimer.Start();
}
private void MyTimer_Tick(object sender, EventArgs e)
{
MessageBox.Show("The form will now be closed.", "Time Elapsed");
this.Close();
}