It was usable in '98 as well and is available in XP. You can call another PC and chat as well as transfer files. I must admit to not trying this with XP but it worked in '98. It could also be used to share a desktop. XP has a newer client for that purpose.
I still have win98 on several computers on my LAN. My wife just got a machine running XP PRO. our LAN functions properly, but we would like to be able to send messages to others on network ( beats shouting or walking from room to room at diner time, etc.). Is there a program available that will work for 98, ME and XP PRO to send messages back and forth? or do we have to leave her out of message loop and install intercom setup?