I use Firefox 2.0 for so long and keeps a copy of it always
I just tried version 3 sometimes before and uninstalled because I hated its appearance and slow loading of the addressbar history. I use Celeron machine on 256MB RAM.
That's a pic of my screen shot of firefox options if you look for yours all them boxes will
be checked if you uncheck them your firefox will run faster
now if you can't find that I feel for you
It's under tools firefox spends most of it's time checking for updates turn that off and it faster they say it speeds start up
too. It works good for me The ideal came from firefox form.