Did you also delete the Firefox program folder?

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

• Download the full Firefox installer and save the file to the desktop
  https://www.mozilla.org/en-US/firefox/all.html

If possible uninstall your current Firefox version to cleanup the Windows registry and settings in security software.

• Do NOT remove "personal data" when you uninstall your current Firefox version, because this will remove all profile folders and you lose personal data like bookmarks and passwords including data in profiles created by 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 NOT to remove personal data when you uninstall Firefox as that will remove all Firefox profile folders and you lose your personal data.

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

I did uninstall the program and then I followed the directions and removed the folder under program files x86. Then I used the link for the desktop version as shown above however I still get the same message when I try to open. I also have another browser that I use as a back up that I cannot open that is not firefox.

[Maybe check for issues caused by a MS update.

Microsoft ships replacement patch KB 2993651 for KB 2982791 http://www.sevenforums.com/news/343281-what-went-wrong-microsoft-s-august-updates.html

The bad update showed as failed and never installed. The corrected update did run successfully. I just ran any new updates as well but still won't work. Internet Explorer is not opening either. No error message with it just starts to open and then closes. I only use as a back up. My main browser is Firefox but still getting the same original error message. I am going to try a system reset to see if that helps.

Is it too late to suggest a backup of your active profile folder? This article has suggestions on that: Back up and restore information in Firefox profiles.

I searched around on the web and read some threads on this dating back 5-6 years. It may be related to the Windows installer having crashed trying to install something. Does that sound relevant at all? However, I'm not sure how you actually clean that problem up.

This may help;

Welcome to the Microsoft Fix it Solution Center {web link} Find automated solutions for your issues

I am convinced at this point it is due to a windows update. When I restored my computer back to 8/18 Firefox worked find. Then updates apparently automatically loaded overnight and once again it didnt work today. The bad one listed above failed to loan and the updated one ran today but still got the same error message. KB 2993651 for KB 2982791. I restored once more back to 8/18 and turned off updates. I am not sure how to know which update is effecting firefox. I guess I will have to try them one at a time and then try the fix it solution center to figure it out. Thanks everyone for your input.

See also:

• http://www.sevenforums.com/news/343281-what-went-wrong-microsoft-s-august-updates.html

Exactly the same problem. Neither Firefox nor Internet Explorer will open. But Chrome (which I hardly ever use) does open and function. That may be an important clue?

I cannot do anything with the profile because I cannot open firefox. Not even using run "firefox.exe -p".

Same issue. Still no solution!

I would like you to try this; Start the Windows Updater. Make sure it does a scan of your system. Once the list is ready, select the option to show you what is being updated. DO NOT update at this time. Please post the list of updates here.

Open your firewall program. Go to the page that lists the programs that are allowed to access the web. DELETE ALL of the entries. Reboot.

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

• http://www.bleepingcomputer.com/tutorials/how-to-start-windows-in-safe-mode/

Do a malware check with several malware scanning programs on the Windows computer. Please scan with all programs because each program detects different malware. All these programs have free versions.

Make sure that you update each program to get the latest version of their databases before doing a scan.

• Malwarebytes' Anti-Malware:
  http://www.malwarebytes.org/mbam.php
• AdwCleaner:
  http://www.bleepingcomputer.com/download/adwcleaner/
  http://www.softpedia.com/get/Antivirus/Removal-Tools/AdwCleaner.shtml
• SuperAntispyware:
  http://www.superantispyware.com/
• Microsoft Safety Scanner:
  http://www.microsoft.com/security/scanner/en-us/default.aspx
• Windows Defender:
  http://windows.microsoft.com/en-us/windows/using-defender
• Spybot Search & Destroy:
  http://www.safer-networking.org/en/index.html
• Kasperky Free Security Scan:
  http://www.kaspersky.com/security-scan

You can also do a check for a rootkit infection with TDSSKiller.

• Anti-rootkit utility TDSSKiller:
  http://support.kaspersky.com/5350?el=88446

See also:

• "Spyware on Windows": http://kb.mozillazine.org/Popups_not_blocked
• https://support.mozilla.org/kb/troubleshoot-firefox-issues-caused-malware