Mozilla even has a skin template that can make Mozilla look just like IE. Even the people at Mozilla realize how stubborn users can be when it comes to switching products.
http://kodu.neti.ee/~tar/mozilla.html

A helpdesk's nightmare!

helpdesk: What browser are you using?
luser: Internet Explorer
helpdesk: OK, tools, internet options...
luser: wait... its not there...
helpdesk: Its not there?! What do you mean its not there... it has to be there...
luser: I'm telling you, internet options is not under tools...
helpdesk: Are you sure you're using Internet Explorer?
luser: yes! It has the "BIG E" thats Internet Explorer... right?
helpdesk: um... let me get back to you