Fresh from WinXP News, try this:
Disable the Windows Messenger Service to Stop Messenger Spam
We still get a lot of mail from WinXPnews readers who have problems with Windows Messenger Service spam. You need to stop the Windows Messenger Service to stop the spam. Here's how:
Click Start and click the Control Panel.
In the Control Panel window, make sure you're in Classic View. If you're in Category View, click the link on the left side of the window that says Switch to Classic View.
Double click on the Administrative Tools entry in the Control Panel.
In the Administrative Tools window, double click on the Services entry.
Scroll through the list of entries in the Services window and find the one named Messenger. Double click on the Messenger entry.
In the Messenger Properties (Local Computer) dialog box, click the Stop button. You'll see a clock displayed while the service stops.
Click the down-arrow in the Startup type drop down list box and select the Manual entry. Click Apply and then click OK.
Congratulations! You'll never see Messenger spam again!