Instead of close down the app, the app hide in the system tray instead.
Will require a NotifyIcon and a ContextToolStrip

public bool ExitTime = false;

        private void FrmMain_FormClosing(object sender, FormClosingEventArgs e)
        {
            if (!ExitTime)
            {
                e.Cancel = true;
                this.Hide();
            }
        }

        private void ntIcon_DoubleClick(object sender, EventArgs e)
        {
            this.Show();
        }

        private void exitToolStripMenuItem_Click(object sender, EventArgs e)
        {
            ExitTime = true;
            Application.Exit();
        }

Some more useful articles for you

• Did you know about db4o – a brilliant object oriented database
• Application to fix case sensitive problem when move your website website to linux server