Simply put, Mozilla Firefox is actually very umm ... (I can't think of a word to use instead of portable because it's not the correct term for this) environment independant (that'll do
) anyway, as in you can move the Firefox directory about and the program will still run.
The few registry entries are to do with the location of the users profile, and in Portable Firefox these are hard-wired into the program as \Data\Profile . You can actually copy the profile directory from inside your personal Application Data folder to the portable profile directory and have your portable firefox set-up *exactly* the same as it is on your local computer.