First, download and install the free Jabber client called Psi. It’s a fine Jabber client, and you might want to keep it, but you won’t need to once you’ve set everything up. The Psi wiki has a great step-by-step for connecting to Google Talk. Follow their instructions and you’ll be able to see your Google Talk contacts. 

Next, go to Service Discovery and browse the Jabber server and you’ll see the transports available.

Click on a transport and Psi will gather data.

Right-click on a transport to register. Registration involves entering your username and password for the given IM network. Once you do, Psi will connect to that network and retrieve your contacts. You can also add new contacts.

Once I had “registered” each of my IM accounts, I had a lot (hundreds?) of system messages. 

Basically it asked me to confirm that I wanted to add each of these contacts. Once I did, they showed up in my Psi contact list.

Now exit Psi and fire-up Google Talk. You’ll have all your IM contacts right there on your Google Talk contact list.

Once you’ve done so, you can chat with your friends on AIM, Yahoo, ICQ, MSN — all using Google Talk. You can also add contacts directly within Google Talk. Just use the format [screenname]@[transport.dns.name]. For example, to add my MSN screen name you would enter mycontact% hotmail.com@msn.jabberserver.xx or myicqnumber@icq.jabberserver.xx 

Enjoy it