in .net 2 if you want to show your application in system tray. you need to add notify icon to your application and set the "ShowInTaskBar" property to False. now you have the notify icon in the system tray. my problem was I could not show the form if I double click on the notify icon. I tried to BringToFront() which works but it did not work under this situation. anyway here is the solution:
private void notifyIcon1_MouseDoubleClick(object sender, MouseEventArgs e)
this.Visible = true;
I know that bringtofront function does not work but I like to see my code this way more clear :) now Activate() works perfectly.