Let me start by saying: before Firefox converted users of 32-bit Firefox to 64-bit Firefox, of course 32-bit Firefox was installed into the Program Files (x86) directory like other 32-bit programs. When Firefox converted (around the days of Firefox 54), it kept using that same folder for upgrades. Over the past year, a number of users have had an upgrade glitch that created a new installation in the regular Program Files folder used for 64-bit programs, resulting in a dual install. So we have an idea of how to sort this out.

The first thing to try is switching your newer installation to using a different profile. Here's how:

Make sure your older installation is not running. Launch your newer installation, and then:

Version Check

You already confirmed that your newer install is 85.0.2, the latest release, so Firefox shouldn't raise any objections about switching profiles.

Profile Manager Page

Inside Firefox, type or paste about:profiles in the address bar and press Enter/Return to load it.

This page should list at least two profiles and could list many. (Each profile has two folders and one or more buttons. Do not use any Remove buttons!)

The profile that Firefox is currently using will have this:

This is the profile in use and it cannot be deleted.

This is the profile that doesn't have your data.

For the other profile (or one of the other profiles), check whether it is the one you prefer by clicking its Launch profile in new browser button.

If it isn't what you want, simply close that new window.

If it IS what you want, back on the about:profiles page, click the Set as default profile button for that profile so Firefox uses it automatically at the next startup.

Exit Firefox and restart your newer installation. Did it work?

Now, how to get rid of the unnecessary Program Files (x86) installation without doing any damage. Let's return to that after fixing the profile issue.

Thank you but I think you are missing the point or I am confused. Define “installation” . There is no second “installation” – if only that was the problem. There is only one FF in the programs list. Are you saying that FF is separately installed in two different directories (the new blank one being the unchangeable FF default and the other being the preferred x86 directory?

OMG! YES! That worked! U R A CHAMP! Superbly communicated! Now then what should I delete from where? I presume I should delete the old short cut pinned to the task bar? And what else should I delete or uninstall and how? I presume all Mozilla in the x86 related directories? Again thank you! What a relief! Please advise as to clean up.

And, oh yes, will this effect any of my add-ons and plug ins?

So far, so good.

Yes, change your shortcut.

Do you have Microsoft Office on your computer? If so, click a link in Word or Outlook to make sure it is opening the correct Firefox. It can be the most stubborn app when it comes to changes of default browser.

If that isn't a factor, you can delete the old Firefox installation under Program Files (x86) so it can't accidentally run again. It would be extremely unusual to be running add-ons from that folder which aren't part of Firefox's own installation. However, if you remember ever creating Autoconfig files (like mozilla.cfg) or a policies.json file in this older Firefox program folder, you may want to rescue those before deleting.

Thanks again. No I do not have Outlook or MS Office and the new FF launches fine from links in Word Perfect (Corel) and Windows Live mail (WLM). I just deleted the old FF shortcut form the task bar and re-pinned the new one. It’s all good! I do not recall creating any .cfg files. Not sure what x86 files you want me to delete. Can you be more specific.

BTW (if it falls within your expertise) the same Win 10 upgrade caused a problem in WLM. I receive mail all just fine and links work but I can sent or reply. “A problem occurred opening this file....” WLM was working just fine in Win 10 till this update and, of course, Microsoft will provide no support and, given the level of support I’ve gotten for Win 10 they are, quite frankly, a disgrace. I want to avoid buying Office or Outlook! So if you know a fix that would be great but please clarify what you suggest me to delete from the C:\Program Files (x86). There is an ‘uninstall’ there but I presume that should be avoided. Do I delete all Mozilla related files from that directory?

Again, tank you VERY much. SO appreciative!!!!!

I think you can remove

C:\Program Files (x86)\Mozilla Firefox

but you could test the theory by renaming it to

C:\Program Files (x86)\OldFirefox

and monitoring for a few days. If there are no objections by other programs, you could dump the folder.

Will do. Thank you again... very much.

Btw: Mozilla Thunderbird and Mozilla Maintenance Service are also in the Program Files (x86) directory. I do use Thunderbird. Does the FF issue portend similar problems with Thunderbird? And since I have a 64 bit commuter do I really need the x86 directory at all since that’s for 32 bit computers?

I have not heard of any double-install issues with the maintenance service or with Thunderbird. There definitely are a lot of 32-bit programs that all of us 64-bit Windows users still rely on, so I wouldn't delete anything else there.

Thanks again! All seems good!