These ads are using Messenger Service.
Messenger Service is a valuable tool many use.
Like many tools, it can be exploited.
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.
Internet Connection Firewall will not work if you have AOL.
AOL is not compatible with Windows XP Internet Connection Firewall
(ICF)
If you have AOL, you should contact AOL and/or get a 3rd party
firewall:
http://www.zonelabs.com/store/content/home.jsp
http://www.symantec.com/sabu/nis/npf/
Disable Messenger Service:
Start/Control Panel, click Administrative Tools, click Services.
Go down to "Messenger".
Right click "Messenger" and select Properties.
Then under Start-up select DISABLE
Click OK and follow prompts
