Fly Mail is a tiny program that lets LAN users send instant messages through TCP/IP. It's free but quite robust. It runs in the background, requires no installation, and offers a choice of English, Russian, German or custom for the interface. You can print and scroll through the sent as well as received messages, you can send files. Navigation is very straightforward, so the lack of documentation shouldn't be a problem. With Fly Mail running, you simply click on Send New Message to choose someone on the network and type a quick note. Optional audio alerts can signal that a new message has arrived. Options to pop up when messages arrive and to run at startup can be easily toggled on and off.