Gmail Notifier

Google provides a special desktop program for both Windows and Mac users that notifies you when new e-mail arrives in your Gmail account. It remains invisible until mail arrives in your Gmail inbox. Then, a small window appears from the taskbar alerting you to the new message.

You can click this notification to launch Gmail and view the new message. This service is automatically installed when you install Google Desktop.

Cross-Ref 

See Chapter 11 for more information about installing Google Desktop.