You might be interested in FEBE then:
http://customsoftwareconsult.com/extens ... /febe.html
It's a tool to allow you to backup your entire Firefox2/3 profile, or portions thereof. You'll need to go in and setup the directory to backup to and such, and I highly recommend you set it up to backup individual items rather than the entire profile.
When you backup the entire profile it can't actually restore it directly, you have to rename the backup file with a .zip extension (or just open it in winzip/7zip etc in a way that allows you to specify the file as a zip32 format file) and then extract it over your existing profile. The problem is that there are certain files that will still either be encrypted or have the wrong profile string (the string matches the string of characters you'll see for your profile's subdir under C:\Documents and Settings\%Username%\Application Data\Mozilla\Firefox\Profiles or etc) and things won't work correctly.
When you backup Firefox's individual components, you can just reload your passwords, bookmarks, form field data etc using FEBE. Extensions & Themes you can just drag & drop to the 'addon' windows (tools>addons) manually so it's not even necessary to use febe for them (hint, just drag them all at once, restart FF & wait for them to install).
Since I do a lot of web-based work, I schedule a weekly backup in FEBE and have another sheduled process that then archives this to my NAS storage an hour later (for burning to disk later etc).