Customization in FF3 vs FF4

Our company dictates that IE must be used, the reasons for I wont even get into. prior to FF4 a bunch of geeks just edited the all.js file of FF and happily went along our way using FF without BB knowing or caring.

With FF4 I dont know or see what they did because I cant find that file that used to be located here C:\Program Files\Mozilla Firefox\greprefs\

SO I have to use FF3 until we can find how we can trick the perimeter into thinking FF is no longer an "illegal browser"

Any help would be great.