This is an IRC server for windows and linux
IRC is the standard protocol for chat on internet
Even though IRC is only text, it is popular. Right now, hundreds of thousands of people are using irc, most of them are on 4 big nets: Undernet, EFnet, IRCnet, and Quakenet.
running your own IRC server is very useable for different kinds of communication on internet or LAN, such as:
http://bewareircd.sf.net/ Download source code at SourceForge
Note that beware ircd has and has always had stability problems. it can be used perfectly fine for testing or a small irc server, and it is probably one of the better choices you have on windows. but with many local users (not sure how many) it will have problems such as excessive cpu usage, hanging/crashing, etc. if you need a server for many users or you find stability and uptime important, you should run a real ircd, on a real OS.
links (everything in this list is free and open source):
i'm not going to give support using email anymore. if you need support, come to irc, maybe someone is willing to help. note: you must put the word "P10" in the subject, otherwise the email will be filtered as spam.
irc: #bircd at irc.quakenet.org
Also check my other project, BGB gameboy emulator.