How to stop the Pop-Up Spam - Messenger Service:
Disabling the Messenger Service
To remove the ability for anyone to pop up messages on your computer, you
can disable the Messenger service. Its easy to reverse at a later time if
you wish to do so.
Keep in mind that you are advised to check with your computer support staff
before disabling any service so that you do not inadvertently disable a
service that your department uses.
Windows XP
Click Start->Control Panel
Click Performance and Maintenance
Click Administrative Tools
Double click Services
Scroll down and highlight "Messenger"
Right-click the highlighted line and choose Properties.
Click the STOP button.
Select Disable or Manual in the Startup Type scroll bar
Click OK
I hope it helps - please write results..
arth