Do I need all these instant messaging programs?

The short answer is that for the most part, the major instant messaging services can not talk to each other. That means:

• You must use MSN Instant Messenger to IM with your friends who use MSN Instant Messenger

• You must use AOL Instant Messenger to IM with your friends who use AOL Instant Messenger

• You must use Yahoo Instant Messenger to IM with your friends who use Yahoo Instant Messenger

Now, there are exceptions.

First you should be aware that MSN Instant Messenger, Windows Instant Messenger, and Windows Live Messenger are really all the same instant messaging service. They're simply different programs that all communicate on the same instant messaging network. So those programs can all be used with each other.

The other exception is that last year Microsoft and Yahoo cut a deal that makes it possible for their two systems to interoperate, if you use the appropriate client program. That means if you set things up correctly, you can IM to a Yahoo Instant Messenger friends using MSN Instant Messenger.

But right now, that's about as good as it gets.

Even though you need to use the matching service to IM your friends on that service, you can use a single program to do it. Programs such as Trillian and Gaim allow you to install a single program to communicate using all the major IM services. You still talk to AIM users using AOL's service, and MSN users using Microsoft's, but you don't have to install and run a second (or third, or fourth) program to do it.

Caveat: Programs like Trillian and Gaim may be considered illegal, or a violation of the IM services terms of service. The argument is that the IM protocols are not actually made public, and using these programs bypasses the advertising that is displayed in the services native clients - thus denying them of the revenue they're entitled to for providing their services for free. You'll need to make you own decision on whether to use these types of clients.