Rated 5 out of 5 stars
Just logged in to thank Ramon for the FF4 tip. I used 7-Zip to extract the files, made the changes then re-zipped them. I had to rename the resultant file from .zip to .xpi but then just installed like a normal addon.
My grandchildren are very grateful 'cos they can now get even more rubbish games icons on my toolbar!!
I'm using Windows 7 Home Premium 64 bit.