Firefox only prevents popup windows that try to open in Firefox. Firefox has no prevention against popup windows in Internet Explorer.

You can not delete internet explorer completely from your computer because your OS kind of needs it. All the windows you open, your My Documents nad My Computer folders... all run with IE. So you can't delete it completely. But what I did was delete ALL shortcuts I could find that lead to IE and then I renamed the FireFox shortcut to "Internet" so that if I had visitors or friends over who wanted to use my computer, they would know to use Firefox to get on the internet instead of searching around on my computer for internet explorer.

BUT if you are getting popup windows and do not even have any browser window open, you most likely have spyware. I recommend Ad-aware and Spybot Search and Destroy. Run them and update them RELIGIOUSLY! I run mine at least three times a week, if not once a day. It will find stuff you didn't even know you had