If you want a private chat with a friend or client on you Network, you don't need to download any fancy program!
All you need is your friends IP address and Command Prompt.
Firstly, open Notepad and enter:
set /p n=User:
set /p m=Message:
net send %n% %m%
Now save this as "Messenger.bat". Open the .bat file and in Command Prompt you should see:
After "User" type the IP address of the computer you want to contact.
After this, you should see this:
Now type in the message you wish to send.
Before you press "Enter" it should look like this:
Now all you need to do is press "Enter", and start chatting!