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!

Try to boot the computer in Windows Safe mode with network support (press F8 on the boot screen) as a test to see if that makes it possible to delete the Firefox program folder to do a clean (re)install.

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

I have a problem with Mozilla on my PC.. It sounds like this: I install Mozilla on PC.. usually i install latest version and I can enter mozilla .. it works great.. but after i restart, shutdown or log off my PC it doesn't work... and i must install it again. Please help me. . This problem isn't only at mozilla.. there are many programs that are the same.. and it doesn't stop here.. If i download something and i restart my PC, I can't open that file.. i can double click that file a thousand times, it doesn;t open.. it doesn;t show me anything.. I had this problem once.. i reinstalled my windows.. but the problem is still here.. I mention that.. when i reinstalled my windows.. i choosed "Quick format" .. might be this the cause?

Which security software (firewall, anti-virus) do you have?

Boot the computer in Windows Safe Mode with network support (press F8 on the boot screen) as a test to see if that helps.

Do a clean reinstall and delete the Firefox program folder before (re)installing a fresh copy of the current Firefox release.

Download a fresh Firefox copy and save the file to the desktop.

• Firefox 21.0: http://www.mozilla.org/en-US/firefox/all.html

Uninstall your current Firefox version, if possible, to cleanup the Windows registry and settings in security software.

• Do NOT remove personal data when you uninstall your current Firefox version, because all profile folders will be removed and you will lose all personal data like bookmarks and passwords from profiles of other Firefox versions.

Remove the Firefox program folder before installing that newly downloaded copy of the Firefox installer.

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

• It is important to delete the Firefox program folder to remove all the files and make sure that there are no problems with files that were leftover after uninstalling.
• http://kb.mozillazine.org/Uninstalling_Firefox

Your bookmarks and other personal data are stored in the Firefox profile folder and won't be affected by an uninstall and (re)install, but make sure that "remove personal data" is NOT selected when you uninstall Firefox.

If you keep having problems then also create a new profile.

• http://kb.mozillazine.org/Profile_folder_-_Firefox
• http://kb.mozillazine.org/Profile_backup

• http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Clean_reinstall