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Firefox 52.7.2esr will not run, could not load XPCOM. Also will not uninstall. On a Vista PC

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  • Last reply by MilfordKen

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I have been using Firefox on my Vista PC with no problem until I ran the update from 52.7.2 to 52.7.3 . Now I cannot start Firefox and I get the message - could not load XPCOM . I have down loaded 52.7.3esr ready to install but I am unable to uninstall 52.7.2 even if I use the helper.exe file. Please note I am sending this on a W8.1 computer, not the one that is giving me the problem.

Chosen solution

Firefox 53.0 and later including the current 59.0.2 requires Windows 7 and later to run. Also 64-bit for Windows (Win64) and Firefox version requires 64-bit Windows 7 and later to run.

For Windows Vista You need the 32-bit Firefox 52 ESR (Windows 32-bit) in which the current is at https://www.mozilla.org/firefox/organizations/all/

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MilfordKen said

Please note I am sending this on a W8.1 computer, not the one that is giving me the problem.

Odd. Your systems details says; Windows Vista


Let’s do a full clean re-install;


Download Firefox; Extended Support Release {web link} ESR Notes System Requirements


Save the file. Then Close Firefox.

Using your file browser, open the Programs Folder on your computer.

Windows: C:\Program Files C:\Program Files (x86)

Mac: Open the "Applications" folder. https://support.mozilla.org/en-US/kb/how-download-and-install-firefox-mac

Linux: Check your user manual. If you installed Firefox with the distro-based package manager, you should use the same way to uninstall it. See Install Firefox on Linux; https://support.mozilla.org/en-US/kb/install-firefox-linux

If you downloaded and installed the binary package from the Firefox download page, simply remove the folder Firefox in your home directory. http://www.mozilla.org/firefox#desktop ++++++++++++++++++++++++++++ Look for, and remove any Mozilla or Firefox program folders. Do not remove the Mozilla Thunderbird folder if there is one.

Do Not remove the profiles folder.

After rebooting the computer, run a registry scanner if you have one. Then run the installer. +++++++++++++++++++++++++++ If there is a problem, start your Computer in safe mode and try again.

http://encyclopedia2.thefreedictionary.com/Linux+Safe+Mode This shows how to Start all Computers in Safe Mode; Free Online Encyclopedia

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Thank you for your email.

Perhaps I did not make myself clear, so I will try again. My problem is on a Windows Vista computer and Firefox will not start at all, I get the 'could not load XPCOM' message.

I contacted you using my Windows 8.1 laptop because I could not do it via the Vista PC.

I followed your email instructions by downloading using the laptop and copied the installer to the PC using a USB stick.

When I tried to run the installer I got a message that it was for Windows 7 or later so it would not run.

I would be grateful for any other help you can give.

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Chosen Solution

Firefox 53.0 and later including the current 59.0.2 requires Windows 7 and later to run. Also 64-bit for Windows (Win64) and Firefox version requires 64-bit Windows 7 and later to run.

For Windows Vista You need the 32-bit Firefox 52 ESR (Windows 32-bit) in which the current is at https://www.mozilla.org/firefox/organizations/all/

Modified by James

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Thank you. This was what I tried to do in the first place but I thought I would need to uninstall my existing Firefox installation before running the new install. The uninstall would not work hence the reason for my request for help. I am now using Firefox again on my Vista PC.