From resident expert - the-edmeister "No it can't be removed." He specifically warns against using a method suggested in Yahoo Answers which will break Firefox security features.

Depending on user skills e.g. if a child is over about 8 he can download and uninstall versions of any browser including another Firefox in no time flat. A password on your computer is about the only solution. There are ways around any method I've heard of.

If we are talking about children, the usual suggestion is to have them working(with headphones) near the family.

For more discussion try the Search Firefox Help box above.

A little more if there is anyone out there. Win7 has a lot of apparently well-regarded advice on parental controls. I presume Vista would have an earlier version which would be well worth reading.

Firefox does not respect Vista & Win7 Parental Controls as far as Private Browsing in Firefox is concerned.

This Bug was filed in 2008, and there hasn't even been a comment about that issue posted by a developer in over a year.
https://bugzilla.mozilla.org/show_bug.cgi?id=471658