If the Tracker or Deskbar should ever crash on you, or if your icons suddenly all turn into plain blue squares (a rare, random, and mysterious occurence), you can „restart the desktop“ easily, without needing a Terminal window open.
Hit Ctrl+Alt+Del to bring up the Team Monitor. If you see a „Restart the Desktop“ button, click it. If you don’t, select either the Tracker or the Deskbar in the threads list and kill it off. When you bring up the Team Monitor again, the „Restart Desktop“ button should be there.
An easier way to kill off the Tracker manually might be to use the Vulcan Death Grip.