patrickjdempsey wrote:Menu > Help > Troubleshooting Info > click Open Containing Folder.
Close Firefox.
Open the pref.js file using a text editor and get rid of those entries.
Also make sure you don't have a user.js file, if you do open that up and look for those entries.
There have been reports of the Skype toolbar installing nasties with it so you might try disabling that and repeating.
Babylon had wormed its way onto my system despite me unticking all the relevant boxes during installation of Hypercam2 some time ago. I had managed to get rid of visible signs of it but accidentally came across the about:config entries whilst looking for something else - horror
Before doing anything else I uninstalled Hypercam2 via Add/Remove (I wish I'd used Revo but just didn't think!).
Patrick's solution has worked for me, once I managed to access Notepad (in Windows7 it's in Windows>System32) to use as "text editor". Babylon was in prefs.js (I deleted entries and saved file) and user.js (I deleted that file entirely as there was nothing in it besides Babylon entries).
For extra reassurance I rebooted the laptop and checked about:config - it's well and truly GONE!
Thank you, Patrick