Microsoft appear to have dropped the “net send” command in Windows 7/vista.You can use one of the following alternatives
You can see the following options how to use msg
2) sent Utility
Sent is a small console utility intended for sending net send messages over local area networks using command line. The utility can be used as a ‘net send’ command replacement on versions of Windows, that do not support this command (7, Vista, 98, 95) or just as an improved ‘net send’ command with additional features.
Main features are:
* sending personal messages using computer’s network name, user’s login, nickname
* sending broadcast messages using workgroup or domain name
* sending a message at once to several recipients
* batch mode of operation with ability to load messages and recipients from a text file.
* timeout settings
For message transmission the Sent uses full implementation of the protocol, that is used for message exchange by software products like Microsoft WinPopup, Windows Messenger Service (net send), etc. Therefore the Sent is fully compatible with them.
Download sent utility from here
You can check how to use sent from here