Windows Live/MSN Messengers and Yahoo Messenger US version supports voice chat. Gtalk users prefer the less bloated client that also provides voice chat features.

Here, is how to make voice calls between GTalk and Yahoo Messenger - from Gtalk or Yahoo Messenger using the Gtalk2VoIP service. Both services can also voice chat with MSN (Windows Live) users.

If you use Yahoo Messenger :

1. Start your Yahoo Messenger - Add a new friend - gtalk2voip@yahoo.com
2. You should see a “friend” on your list. This is a bot. On the other side, is an automated system.
3. To call another Yahoo or Gtalk user , send the following message to your new bot friend :

CALL someuser@gmail.com to call Google Talk user someuser@gmail.com, or

CALL someuser@hotmail.com to call MSN/Live Messenger user someuser@hotmail.com

CALL someuser@yahoo.com to call Yahoo Messenger user someuser@yahoo.com

4. You should get a phone call yourself. Recieve it and listen to the rings, as you are connected to another Gtalk or MSN or Yahoo user.

Type HELP to the bot for more detailed help and functions.

For Gtalk users, the procedure is identical except you have to add/invite “service@gtalk2voip.com” to your list.

PS : For those of you know about SIP , CALL someuser/number@sipphonedomain.com will allow connection to SIP phones too!
If you don’t know what SIP is, ignore this.