You may not have realised this until now but Mozilla Firefox has its own version of the Windows Registry, where all your preferences are stored. In the browser, it can be accessed by typing in the address bar about:config
But what, in the future, if you have to re-install Firefox from scratch? You may have spent a long time tweaking Firefox to get it the way you want it and if you subsequently lose all your preferences, then you would have to start again from the beginning. This would throw me into a fit of rage but I discovered recently there is a way to make a backup of your "about:config" preferences in case anything goes wrong.
Just navigate to your Firefox profile folder in your Windows Explorer . For me, it's under
Documents and Settings -> Mozilla -> Firefox -> Profiles
However, it may be different for you, depending on how you installed Firefox on your system.
When you have located the profile, locate a file called prefs.js. This is the file containing all your settings and preferences. Just copy that file to somewhere safe such as a USB stick , a re-writable CD disk or even just another location on your PC. Remember to update this file on a regular basis with your latest settings.
If you subsequently lose your preferences on Firefox, just drag your copied prefs.js file back into the Firefox profile. Windows Explorer will tell you that a prefs.js file already exists and would you like to replace it with your copied file? Say yes and your preferences will be updated the way you want them again.