System Requirements:
Windows 2000/XP (Home & Pro)
Internet Connection
Microphone and Speakers (For voice calls)
Account by gmail.com

Installation:
Download and Install from here (It's only 900kb) . There is nothing else to mention about the installation procedure as it is pretty simple apart from the fact that you will just have to use your gmail username and password to log-in.

Features:
Google Talk is in position of looking other clients right in the eye. Just like them, it can send instant messages, check your e-mails and now, by utilizing the new facility provided, you can also talk to your acquaintances in real time.

Google Talk is a very simple and easy to use messenger

Call your friends: Speed and quality are the best characteristics of this feature. You can hear the person(s) you are talking with, as if they were in the same room with with no lapses of time to interfere with the process. The only drawback in the case is that communication is accomplished on condition that they are also equipped with Google Talk. Yet, such a course of action is not necessary if instant message communication is required. It goes without saying that all is free.
Small size and a small amount of RAM memory needed: Google Talk is only 900kb and allocates only about 6mb in the memory each time you use it. It is about 3-4 times less than the memory normally needed. However, this is going to change in the final version.

The less RAM memory used by a program, the faster it is going to open and close. This feature is extremely helpful in terms of saving up memory

Check you e-mails without having to login:
With Google Talk you can check for new mails all the time and with just one click you can visit your inbox page. Also, when a new e-mail has arrived, Google Talk lets you read a sample without having to log into your account first. A very useful facility indeed.

With google talk you can check your mails faster that with any other messenger

Supports open standards and is compatible with many clients:
As we have already pointed out, Google Talk uses open standards and as a result it is compatible with many clients, such as the Trillian Pro.