When you reinstall the profiles and preferences are not deleted..

Go for Clean Reinstall

Certain Firefox problems can be solved by performing a Clean reinstall. This means you remove Firefox and any leftover program files and then reinstall Firefox. Please follow these steps one by one:

1. Download the latest Desktop version of Firefox from http://www.mozilla.org and save the setup file to your computer.
2. After the download finishes, close all Firefox windows (click Exit from the Firefox or File menu) and confirm all upcoming messages.
3. Now, uninstall Firefox by following the steps mentioned in the Uninstall Firefox article.

IMPORTANT: On Windows, the uninstaller has the option to remove your personal data and settings. Make sure that you do not check this option; otherwise all of your bookmarks, passwords, extensions, user customizations and other Firefox user profile data will be removed from your computer.

After uninstalling Firefox on Windows, delete the "Mozilla Firefox" program folder, located by default in one of these locations:

• (On 32-bit Windows) C:\Program Files\Mozilla Firefox
• (On 64-bit Windows) C:\Program Files (x86)\Mozilla Firefox

1. Go to the Windows Start menu and click on "Computer".
2. In the Explorer window that opens, double click Local Disk (C:) to open the C:\ drive.
3. Find the "Program Files (x86)" folder or "Program Files" folder.
   • On 32-bit Windows, double-click the Program Files folder to open it.
   • On 64-bit Windows, you will see a "Program Files (x86)" folder AND a "Program Files" folder. Open the Program Files (x86) folder.
4. Look for a Mozilla Firefox folder. If you find one, right-click it and select Delete and confirm that you want to move the folder to the Recycle Bin.

Now, go ahead and reinstall Firefox:

1. Double-click the downloaded installation file and go through the steps of the installation wizard.
2. Once the wizard is finished, choose to directly open Firefox after clicking the Finish button.

Please report back to see if this helped you!

Hello 11111AAAR.M

try to create a new profile : go from Start > Run and type %APPDATA%\Mozilla\Firefox

then find profiles.ini file and rename it to profiles.iniOLD , then when you start firefox again, a new default profile folder will be created and only a single profile, the new "default", will be listed in the Profile Manager.

This new "default" profile doesn't contain any of the profile data or settings stored in your old "default" profile folder, which still exists but is no longer accessible from the Profile Manager.

Your existing Firefox user profile data, which includes bookmarks, passwords, cookies, preference settings and added extensions, will no longer appear in the new profile but you can transfer the data from the old profile folder to the new default profile folder.

see also : Recovering important data from an old profile

thank you

This can happen when the profile that is marked in the profiles.ini file as Default=1 is missing.

• http://kb.mozillazine.org/profiles.ini_file

If there is still a profiles.ini file, but the profile folder is gone then delete the profiles.ini file to force Firefox to create a new default profile.
Otherwise you can create a new profile and use "Choose Folder" to recover an existing profile.

• http://kb.mozillazine.org/Profile_Manager
• https://support.mozilla.org/kb/Managing+profiles

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• https://support.mozilla.org/kb/Recovering+important+data+from+an+old+profile