Update: Note that the program has been last updated in 2009. While it may still work, it is advised to use a program that is updated regularly. One of the programs you can use for that is Google's official Gmail Mail Checker for the Chrome browser. Update End
If you do not want to keep Gmail open in a web browser all the time and also do not like the idea of installing an email client to monitor the Gmail inbox (either because they use to much system resources or pose a risk to privacy) you might want to check out the Gmail mail notifier Gdow.
Gdow is a lightweight portable application that runs quietly in the Windows system tray. It will check the Gmail inbox sporadically and notify you when new mails have arrived. The gmail mail notifier will display the current unread mail count of the Gmail inbox in the system tray and even display mail previews when hovering over the system tray icon.
The notifier has to be configured before it can be used. Among the required settings are the Gmail username and password. You can configure the type of information that are displayed (object, summary, sender's name and address), and the way it is displayed (messagebox, popup balloon, transparent form).
It is furthermore possible to change the mail check interval and enable sound notifications for new mails. The system tray icon contains a link to the Gmail inbox. The way the inbox is opened can be configured in the options as well. Among the options are the possibility to open the inbox in the default web browser or default email client.
Gdow uses roughly 12 Megabytes of computer memory while running. The Gmail mail notifier will run on most Windows operating systems including Windows XP and Windows Vista.
Ghacks is a technology news blog that was founded in 2005 by Martin Brinkmann. It has since then become one of the most popular tech news sites on the Internet with five authors and regular contributions from freelance writers.