The Google Talk downloadable application for Windows offers many features for communicating with your friends and family.
Instant messaging - Chat with all of your Google Talk and Gmail contacts in real time.
Free PC-to-PC voice chat - You can talk to anyone else for free who's online and has the Google Talk client.
Send and receive voicemails - If the person you're calling isn't available, you can leave a voicemail.
Unlimited file transfers - Send files to your contacts. There are no file size or bandwidth restrictions.
Gmail notifications on your desktop - When you're signed into Google Talk, you'll be notified of new messages in your Gmail inbox.