HI   !

Did you download Firefox from here  :

https://www.mozilla.org/en-US/firefox/all

I still keep getting the error message "couldn't load XPCOM

Did you delete the Firefox program folder?

(32 bit Windows) "C:\Program Files\Mozilla Firefox\"

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

If you have any security and/or anti-virus software installed, would you disable it and see if that will makes a difference  ?

I have taken it off and tried to re-install, yet I keep getting the same error message

Maybe you could try to repeat the delete and install steps in Windows Safe Mode. Boot the   computer   in Windows Safe Mode with network support (press F8 on the boot screen) to see if that works.

https://support.microsoft.com/en-us/help/12376/windows-10-start-your-pc-in-safe-mode

Firefox probably tries to install a 64-bit Firefox version when you update.

If you previously used a 32-bit Firefox version then the updater would try to uninstall the 32-bit version.

Did you check for leftover files in both location used on a 64-bit Windows version?

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

Note that there are issues reported with the Firefox 55.0 release and updates have been disabled to prepare a 55.0.1 update.