Try restart the computer and after try again install Firefox.

I tried it but still not installing. After extraction it just died. :-(

Hello,

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!

Thank you.

WARNING: Do not run Firefox's uninstaller or use a third party remover as part of this process, because that could permanently delete your Firefox data, including but not limited to, extensions, cache, cookies, bookmarks, personal settings and saved passwords. These cannot be recovered unless they have been backed up to an external device!

I have tried everything. After I uninstalled Firefox due to unable to update to v26, I was not able to install it at all. So I even tried Windows 7 restore to get v.25 back. After restore, Firefox won't start. I was getting "cannot open XOP" (or something like that) error. Then I tried to uninstall it. It won't uninstall. So I have to manually uninstall the installation directory C:\Program Files\Mozilla Firefox and ran CCleaner to clear the registry. I tried then install newest version 26 (23mb) and also tried the stub and even download the whole v.25. Still the same problem! I have never seen anything like this.

• Start your windows in safemode and remove the firefox existing files.
• Restart your windows and try to install.
• Make sure antivirus is not blocking the firefox installation

I have removed the files in C:\Program Files\Mozilla Firefox prior, what else do I need to remove?

You need remove this folders:

• C:\Program Files\Mozilla Firefox
• C:\Program Files (x86)\Mozilla Firefox

I did that already. I even deleted the Profile directory. Still nothing after extraction.

I believe this is a Firefox installation problem. It must be detecting something and refused to install. I have tried installing other programs and they all installed properly.

I suggest you do a search in your computer with your antivirus and do a test try the firefox portable:

http://portableapps.com/apps/internet/firefox_portable

Thank you . I can install the Firefox portable. What shall I do next?

Close all firefox windows

Try see if there is a process opened in task manager, if yes try close it and try open the installer.

• Did you try install a old version?
• Please,Go to CCleaner, look at tab tools, see if there is a auto initiaze process to firefox.
• Try access app data and search any data related to firefox (folder,cookies,history)

How to access AppData?

Please, sorry my bad english

In case there is a malware related problem, could you do some supplemental scans using the tools listed in this support article: Troubleshoot Firefox issues caused by malware.

• There is no Firefox instance running.
• I have tried to install the newest version.
• No auto initialization of firefox anywhere.
• Appdata does not have any Firefox data

Have been careful and should not have any malware or virus on my PC. But I am running Avasti full scan again just in case.

Meanwhile, is there what if I just use that portable version?

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 installing Firefox.

You can find the full version of the latest Firefox 26.0 release in all languages and for all Operating Systems here:

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

Thanks. I was able to install Firefox in Safe Mode.

However, when I go back to the regular mode, the same issue. I tried to install Malwarebyte and it won't install and it give me an access denied window. That leads me to believe that there is an issue with the permission in the temporary folder. After researching and playing around with the Temporary folder permission, I was able to fix the issue. I don't know how the temporary folder permission got messed up. But now it's fixed.

I would suggest Firefox fix the installation issue. If it can't install due to permission, it should at least give an error message (like Malwarebyte) so that people know it's a permission issue.

I traced the altered permissions for the temp folder to the installation of adobe acrobat xi. apparently adobe made the changes to plug a security hole which they couldn't fix. altering those permissions the way they did affects quite a lot of programs which need to use the temp folders in order to be able to run properly.

hope this info clears things up for you all.

solution. goto the following folder in your computers user account. i.e c:\users\owner\AppData\Local (owner being the name of your account) right click on the Temp folder and select properties. click the security tab at the top. click edit. in the popup box click continue. click add. in the white box type the word Users , starting with the capital letter U. in the users settings ensure that the following has a tick beside it: Read & execute List folder Contents Read now click apply now click ok your programs can now properly use your temp folder again.