After Resetting Firefox you can restore several things such as : Bookmark ,password ,cookies etc...While All of your Firefox settings and personal information are stored in a profile folder named as old Firefox data over Desktop. >>> To know about Profiles see this thread : http://mzl.la/NYhKHH You can Recover things from there By using such steps :

• Create a new Firefox Profile :

See How to create a profile under the ThreadProfile Manager for Firefox

• Now Coping Files between profiles :

                 # Open your Profile folder> menu button > help and select Troubleshooting Information
                 # Under the Application Basics section, click on Show Folder. A window with your profile files will open.

• Now click again to menu button and then exit.
• Right-Click on file(that you want to store) and click on copy .
• Open the new Firefox profile folder.
• Right-click inside the profile folder and choose Paste.

For help see this thread : Recovering data from old profile

These can't get your data back, but will help in the future.

These add-ons can be a great help by backing up and restoring Firefox

FEBE (Firefox Environment Backup Extension) {web link} FEBE allows you to quickly and easily backup your Firefox extensions, history, passwords, and more. In fact, it goes beyond just backing up -- It will actually rebuild your saved files individually into installable .xpi files. It will also make backup of files that you choose.

OPIE {web link} Import/Export extension preferences