How to Remove Those
sent using the Messenger service integrated into Windows 2000 and XP
(try the 'net send' command to see for yourself).
To disable the Messenger service, go to Start --> All Programs --> Administrative Tools --> Component Services. In Component Services, click on Services (Local), then on the right side, find Messenger and disable it.
Note: Not everyone will have Administrative Tools in the Start menu. You need to make it visible under Taskbar and Start Menu Properties (right-click on taskbar --> Properties). The surest way to get to Component Services is to enter %systemroot%\system32\com\comexp.msc into the command line.