So here is my final decision!
I tryed to use winpopup, but the program just didn't want to send messages. All firewalls were down but i still had problems.
I didn't have succes with the Windows chat - it couldn't find the PC iwas looking for.
I installed X-chat, no it is not for me!
The program that took my heart was LAN Chat Enterprise. I had really fun to use it yesterday and today. I think that is very good solution for people using the same LAN.
But if you know other programs, that you think are good then I will have a look at them .
Cheers!!