Are you referring to Messenger Service ads?
Compleatly different from MSN Messenger.
No need to pay for the fix.
For Messenger Service ads:
You need to install or enable a firewall: http://support.microsoft.com/?kbid=330904 http://www.microsoft.com/windowsxp/pro/using/howto/communicate/stopspam.asp
Disabling Messenger Service can be a good idea, but it does not solve
the real problem.
The ads are not the real problem, the ads are only a symptom.
The real problem is open ports that allow unwanted traffic into the
computer.
Disabling Messenger does nothing for the open ports.
The firewall controls the traffic.