Google Talk - Which is Google's approach to instant communications. It's more lite than other competitor Messenger Tools such as YM... You only need to download a small size file from http://www.google.com/talk/ then execute the file... like other 'plug and play ' products.
From my experience... Google Talk gave me a good file transfer process without no file size or bandwidth restrictions (which is much faster than other competitors). If u like to make a voice calls... u will experienced a clearer voice talk such as using fixed line or mobile phone... and it's absolutly FREE....
For beginner user that do not want to go through all the download and install process, you can used it via web but in limited conditions (No download required). For further info go to this link - Google Talk (No download required)
Let me introduce you to all the different ways you can use Google Talk.
Instant messaging — Chat with all of your Google Talk and Gmail contacts in real time.
Free PC-to-PC voice calls — 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. Learn more
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.
Ok folks! enjoy it!
