When or if you upgrade to Firefox 2.0, it is a good idea to back up your profile. This will ensure that if the upgrade gets a bit FUBAR, you will not lose your bookmarks and /or extensions:
To back up your profile, follow these instructions......
To back up your bookmarks and extensions before you upgrade to Ff2.0.
Close all windows running Firefox.
Goto my computer. Click Local disk (C
Click on Documents and Settings.
If you have a user account set up, double click on that user name, if not click on default user.
Click on the "View" button, and then click on "list".
At the top of the window on the tool bar, click the Tools button.
Select options Folder options.
Click on the "View" tab.
There will be a setting called Hidden files and folders, with two circles underneath it.
Click on the "Show hidden files and folders" circle.
Click on "Apply" at the bottom of the window.
This will bring up hidden folders, and you will see a new one called
"Application Data", (usually the second file listed).
Double click on that folder and then scroll down till you reach the Mozilla folder.
Double click Mozilla. Double click Firefox. Single click the "Profiles" folder.
Press the Ctrl+C key, to copy the file.
Minimize the window and then double click on "My Computer". Click on the (C
drive.
Create a file called "Firefox Profile Backup"
Open that file and then press Ctrl+v.
This will copy your profile page to a separate file on your hard drive, so in the event of an upgrade problem, you will not lose your bookmarks and extensions.
If something goes wrong with the upgrade, simply copy and paste the new file into the application data file for the new Firefox.
If for some reason you need to uninstall the new Firefox and revert to the 1.5.0.7 version, you can reinstall it, and then use the file to restore all your settings.
Reference....
http://kb.mozillazine.org/Profile_folder