Gmail notifier

Email programs like Outlook and Outlook Express have an alert that sounds when new mail arrives. I find that particularly helpful, as I have the program set to automatic download, but I don't have to keep checking while I am working on other things. So how can you get a similar feature if you have a Gmail account? One answer is Gmail Notifier, of which there are two versions. There's a Firefox add-on, which adds an icon to the browser toolbar, and a general version which adds an icon to the toolbar at the foot of the Windows screen and alerts you to incoming mail.