Send a message to everyone in your workgroup

This would perform a somewhat similar task as winpopup does.

1. Goto command prompt (to do this, click on the start menu and select run, then type in cmd)
2. Type net send * (your message)

Note: the * would send the message to all of the computeres in the same workgroup as you. To send the message to a specific computer, type in the computer's ip address.