Can't open Firefox. Get message "Couldn't load XPCOM." Please give step-by-step fix.
I have an 8-year-old Vista computer. Firefox has been working fine for years and suddenly went down. I get the above error message when I try to open it from either the desktop or program directory. In the meantime I'm using the version of Explorer that came with the computer but it is old and unsupported. I'm afraid to install the new version because If something goes wrong, with Firefox down, I'll have nothing. I haven't tried to uninstall the bad version of Firefox yet. Can I do it from the Control Panel or is there a better way? Is there a fix for this problem without uninstalling the program? Can I install the new version of Firefox without uninstalling the old one? Will there be two at that point or will the new one overwrite the old one? I am a senior and not very computer literate. I need clear step-by-step instructions that will work. Thanks for your help.
All Replies (3)
First, try uninstalling Firefox and then reinstalling it. If that does not work, uninstall Firefox, remove the profile directory, and then reinstall Firefox.
For specific details, see the original question here with answers: https://support.mozilla.org/en-US/questions/965228
Hello cyberghost,
The instructions by jstar are valid. You can also do a clean reinstall as outlined below.
Certain Firefox problems can be solved by performing a Clean reinstall. This means you remove your Firefox program files and then reinstall Firefox . This process does not remove your Firefox profile data (such as bookmarks and passwords), since that information is stored in a different location.
To do a clean reinstall of Firefox, please follow these steps: Note: You might want to print these steps or view them in another browser.
- Download the latest Desktop version of Firefox from mozilla.org (or choose the download for your operating system and language from this page) and save the setup file to your computer.
- After the download finishes, close all Firefox windows (or open the Firefox menu
and click the close button 
).
- 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.
- Windows:
- Now, go ahead and reinstall Firefox:
- Double-click the downloaded installation file and go through the steps of the installation wizard.
- Once the wizard is finished, choose to directly open Firefox after clicking the Finish button.
More information about reinstalling Firefox can be found here.
WARNING: Do not use a third party uninstaller as part of this process. Doing so could permanently delete your Firefox profile data, including but not limited to, extensions, cache, cookies, bookmarks, personal settings and saved passwords. These cannot be easily recovered unless they have been backed up to an external device! See Back up and restore information in Firefox profiles.
Please report back to say if this helped you!
Thank you.
You need to delete the Firefox program folder to do a clean reinstall.
- (32 bit Windows) "C:\Program Files\Mozilla Firefox\"
- (64 bit Windows) "C:\Program Files (x86)\Mozilla Firefox\"
You can find the full version of the current current Firefox release (39.0) in all languages and all operating systems here:
It is possible that your security (anti-virus) software is causing problems. Try to disable scanning files in real-time in security (anti-virus) software temporarily to see if that makes a difference.