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

Note: You might want to print these steps or view them in another browser.

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).
3. Delete the Firefox installation folder, which is located in one of these locations, by default:
   • Windows:
     • C:\Program Files\Mozilla Firefox
     • C:\Program Files (x86)\Mozilla Firefox
   • Mac: Delete Firefox from the Applications folder.
   • Linux: If you installed Firefox with the distro-based package manager, you should use the same way to uninstall it - see Install Firefox on Linux. If you downloaded and installed the binary package from the Firefox download page, simply remove the folder firefox in your home directory.
4. 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!

I followed your instructions and it still won't open.

If I backup important files and then reformat my hard drive could that work ?

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 helps.

Do a malware check with some malware scanning programs on the Windows computer.
Please scan with all programs because each program detects different malware.

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
• SuperAntispyware:
  http://www.superantispyware.com/
• Microsoft Safety Scanner:
  http://www.microsoft.com/security/scanner/en-us/default.aspx
• Windows Defender: Home Page:
  http://www.microsoft.com/windows/products/winfamily/defender/default.mspx
• 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.

• http://support.kaspersky.com/viruses/solutions?qid=208280684

See also:

• "Spyware on Windows": http://kb.mozillazine.org/Popups_not_blocked

I tried the F8 safe mode with windows support - no luck

I tried

•Malwarebytes' Anti-Malware: •SuperAntispyware: •Microsoft Safety Scanner: •Windows Defender: Home Page: •Kasperky Free Security Scan:

I am getting ready to try spybot search & destroy then Im going to try the rootkit TDSSKiller

Any other suggestions??

I'm not opposed to restoring with the factory recovery discs if that could help

I uninstalled google chrome

I uninstalled and installed a beta firefox

Uninstalled the beta and now I installed v19 again

Now I am getting an error message when I click on the icon "Couldn't load XPCOM"

Make sure to delete the Firefox program folder before installing a new Firefox version.

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

I did the clean reinstall, a bunch of times

I ended up just backing up my important stuff and then I restored the computer to out of box condition

Firefox works now

I have had this problem on and off for 6 months starting from version 16 or 17 (I think). I have isolated the problem to when Firefox has downloaded an update. When Firefox starts it detects an update has been downloaded and is ready to be installed. Firefox attempts to install the update but fails for some reason. This causes Firefox not to start. The problem is a right pain in the ....

The solution is for Mozilla to make sure the Firefox update actually installs or at least reports a problem.

Work around solution is to delete the update folder in your users application data folder. It is not possible to navigate to this folder but On Windows 7/Vista open an explorer window and enter the following folder C:\Users\[your user name]\AppData\Local\Mozilla\Firefox

substitute [your user name] for your real user name.

Under one of the folders you will find a sub folder containing a folder called updates. Find it and delete the folder.

SInce there is no update waiting to install, Firefox will now open when you click on the shortcut.

Can someone at Mozilla fix this update problem so that if the update fails Firefox will still open.

I've had the same problem(s). I tried 19.0.1 and 20.0.1 without success. Reading other posts made me think of bypassing the built-in update and just downloading 20.0.1 from the mozilla site (to another drive just get it out of the way of the standard process)...and success!

I did note something curious on my first try to download 20.0.1 - in the folder created by the download process - C:\Users\<my username>\AppData\Mozilla\Firefox\Updates\ was an install file with the extension .mar What the hell? I have Office on my machine and .mar is recognized as a variant file extension for Microsoft Access!

Though I can't be sure that that was what was blocking the earlier install attempts.

- Bill