Type ' services.msc ' in Run. In menu bar; go to Action > Connect to another computer ... .
Type name of the computer that you want to send message to it. Hit OK.
Then in menu bar; go to Action > All Tasks > Send Console Message... .
In Message part, type your message. Finally hit Send.
Note1: To see the names of computer on the LAN, in menu bar; go to Action > Connect to another computer ... . Hit Browse. In new window, hit Advanced ... . Then hit Find in new window. At the bottom of the window, you can see the Computer's Name.
Note2: You can type ' cmd ' in Run & then type ' net view ' in Command Prompt, to see the compter names on LAN
Note3: Hit OK if any kind of error occur & continue.