glytch,
for your wireless connection, it would probably be cheaper to buy a new combination router/switch. Just don't forget to turn on/up the security for the wireless connection. here are a few links that might help
http://www.pcmag.com/article2/0,4149,844020,00.asp
http://arstechnica.com/paedia/w/wire...802.11b-1.html
onto your note:,
There is a winpopup program that comes with windows (9x) or the net send command (2000/xp) which uses the windows messenger service, but I have found that runing a seperate IM program (for lan use only) works best.
I use realpopup (
http://www.realpopup.it ) on my own home lan because it is small, easily put into the startup and also because it doesn't rely on the windows messenger service. I am sure that you could probably find several programs that can do the same thing but when I originally looked for this sort of program this was the best and only freeware one I found at that time ( few years ago).
I know that you didn't want to have another program, but having people use net send (without some sort of graphical interface/ help from a different program) can be a pain to those not comfortable with using a command line. Hope this at least gives you an idea about an internal lan chat program.