The Cause:

The NET SEND command uses the Messenger service to send messages on the network. This problem occurs because the Messenger service is disabled. By default, the Messenger service is disabled on computers that are running Microsoft Windows XP SP2.

The Workaround:

1-Open Windows Explorer
2-In the left pane, right-click My Computer, and then click Manage
3-In the computer Management window, expand Services and Applications in the left pane, and then click Services.
4-In the right pane, double-click Messenger
5-In the Messenger Properties (Local Computer) dialog box, click the General tab
6-On the General tab, select Automatic from the Startup type list, and then click Apply
7-Under Service status, click Start, and then click OK