Hey guys. I found this forum searching for an answer to the same question, and this is what I learned. If you are using W2K, you can disable the Windows Messaging service, which is what the spammers are using to make those pop-ups appear. Now, just realize that sometimes Anti-Virus software and the print manager use the same service to show messages to the user (the AV notifying you of potential viruses, and the printer manager notifying you of failed print jobs).
To disable the service, go to Start > Programs > Administrative Tools > Services.
Scroll down to Messenger; double-click it to display its properties. Change the "Start Up Type" to disabled, then clik the stop button to disable it now. It should not come back on again.