This information is merely provided to you, how you choose to use it is up to you and could potentially get you into trouble at you school, work, etc. Please only try this on you own network.

Note: this only works on windows computers
1. Make sure that the messenger service is started on the computer that you are sending the message from and the computer that you want to receive the message.
2. Open Command Prompt.
3. In command prompt type in net send (the computer name, IP, user, or domain you want to send the message to, * sends the message to every windows computer on your LAN) (your message, in quotes if it contains spaces).
          You can also view an entire list of different parameters that are available by typing in "net send /?" or "net /?"
Below is an example of a net send command. net send *
If you entered everything properly, you should see the below message in the command prompt window.
net send *
A box similar to the one below should pop up on the recipient's computer (if you did net send *, a box with your message should also pop up on your screen) net send *