Windows Messenger doesn't have Popups though?
A Safer way would be to go into Control Panel, Add Remove Programs; Click Program Settings and Defaults and go to Custom. Untick the allow use of Windows Messenger. That will stop it being used.
Although I doubt its the problem.
Are they Explorer Popups or Messenging Popups? You know like, sized boxes with text in with an OK; which make a bing when they come up and look like an Error Box?
A Knight is sworn to Honour. His heart knows only Virtue. His blade defends the helpless. His might upholds the Weak. His word speaks only truth. His wrath undoes the Wicked.