What would be the best, simplest way for me to chat with a person on another PC on the same LAN? I know Windows has some kind of dialog messaging system built-in, but it's one-way, dialog-only. I just want something that sits in the system tray, that I can double-click to send a message to the other PC, that pops up with a box that they can type in to reply to me, and vice-versa. Preferably something that doesn't require an internet connection. Like those PA/intercom systems that some really fancy houses have? I want that for the computers in this house, text-based.
I wrote such a program myself in Visual Basic several years ago, because all the chat programs I could find at the time (ICQ, MSN, Yahoo) were all internet-based. But I've lost the program, and I don't feel like rewriting it.