An error message about XPCOM missing or about platform version usually happens because of a failed Firefox update that left you with a mixture of old and updated files in the Firefox program folder. This can happen in case security software was keeping a handle of some of the files in the Firefox program folder preventing Firefox from replacing all the files. You need to do a clean reinstall and remove the Firefox program folder to ensure that all files are replaced. You may have to disable security software temporarily in case the problem persists.

You can find the full installer of the current Firefox release (114.0.1) in all languages and all operating systems here:

• https://www.mozilla.org/en-US/firefox/all/#product-desktop-release
• https://www.mozilla.org/en-US/firefox/114.0.1/releasenotes/

Hi Cor-el, Thanks for replying. The actual machine that has the problem is my wife's tablet which is a 32 bit machine. We've never had to "re" install an update and I'm very concerned with having to totally delete the FF folder. I assume it's the "Mozilla" Firefox folder ?? What will happen to all of the settings, bookmarks, personalization, etc.. I did notice that there is an "uninstall" file in the Firefox folder, so is that what I should use ?? I basically need a "step by step" detailed instruction on what I need to do to her tablet. She also uses the free AVG anti virus SW and I don't know how to disable that. Also, when I look at the update options on the site you gave in the reply it offers "two" files for the 32 bit download; Windows 32 bit and Windows 32 bit MSI; don't know which one to chose. So, bottom line I need a very "detailed" step by step instruction to do the deed. Both of us always use the option to install an update as follows: click on the "help" button in FF, then "about" then "update". And we only do that after waiting a week after we've been notified there is an update available due to there usually are "issues" after the release of an update. I started on the internet with "NetScape" back in 1995 and really like staying with FF. So, if you don't mind giving me detailed instructions I would really appreciate it. Thanks again for replying, Don.

This is about removing the Firefox installation in case there are still files present in this folder after Firefox is uninstalled.

Your Firefox personal data like bookmarks and cookies and logins is stored elsewhere.

Firefox uses two locations in the hidden "AppData" location for the Firefox profile folder. One location in "AppDataRoaming" for your personal data (e.g. bookmarks) and another location in "AppDataLocal" for temporary files like the disk cache.

• https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data
• https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles

Hi, thanks for getting back to me. I'm glad that all the personal info will remain OK. So, do I use the uninstall file in C:\program files\mozilla firefox\uninstall to remove the corrupted version ?? Then download the latest version of FF. I'm writing to you on "my" desktop, but will be downloading the file from my wife's tablet via using MS Edge to download the file and put it on her desktop. The URL you gave me for the latest downloadable file says "desktop products". Is there a different file for "tablets" 32 bit ?? Sorry for all the questions, but I've not done this process before. Any hints on things I need to look out for would be appreciated. I don't want to install the wrong file, and I hope the system won't allow that if I do download the wrong one. Thanks again, Don

Is the tablet running a full desktop version of Windows 10? In that case, it's just the normal download you can get from this page (you can select between 32-bit and 64-bit):

https://www.mozilla.org/en-US/firefox/all/#product-desktop-release

No need to run the uninstaller. The folder that has the mix-up usually can be found under one of these two paths:

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

You can rename that folder to OldFirefox (so you have it just in case you need to look in it for some reason) and then run the new installer download. The installer should detect your current profile folders (under C:\Users) and reconnect with them seamlessly.

Hi Jscher2000, Thanks for answering my problem. Yeah, the FF folder is in Program Files\mozilla firefox. I've been to the site you attached and when I click on the download questions for which file I want (which is 32 bit) it offer "two" choices; Windows 32 bit and Windows 32 bit MSI. I assume I will want the "first" one which is just the "plain" 32 bit with "NO" MSI which I don't know what that means ?? That's a good idea about just renaming the current folder (OLD Firefox); if something goes wrong at least I can go back to that folder. But, it's really of no use now as I can "NOT" open FF with the current error. I would like to export the bookmarks just in case something goes wrong, but I need to be able to "open" FF to do that. So, if everything goes right when I install the new download I will eventually want to delete/uninstall OLD Firefox. So, do I click on the "uninstall" folder and will it delete everything or will I need to actually "delete" the folder "after" I've successfully installed the new download. Will the "uninstall" option work properly with the folder it's in has been renamed to "Old Firefox" ?? Also, to answer your question about the tablet; Yes, it does have a full desktop W-10. Please give me all the hints on this process you can as I really need this go right the first time. It's my wife's tablet and she now has to use MS Edge to do her thing and she doesn't like Edge anymore than I do. Thanks again, Don

Hi Don:

> ... it offer "two" choices; Windows 32 bit and Windows 32 bit MSI.

MSI is a slightly different packaging option, but the program is the same.

> I would like to export the bookmarks just in case something goes wrong, but I need to be able to "open" FF to do that.

You can copy files from your profile folder to a backup location. First turn on viewing of hidden files and folders. Microsoft has the steps here: https://support.microsoft.com/en-us/windows/view-hidden-files-and-folders-in-windows-97fbc472-c603-9d90-91d0-1166d1d9f4b5

Then type or paste the following in the Windows 10 search box (on the task bar or start menu, usually):

%APPDATA%\Mozilla\Firefox\Profiles

You may find multiple profile folders here. In each one that you've used actively, there should be a bookmarkbackups folder with compressed (.jsonlz4) files. They have the creation dates coded into the file names, so you should be able to grab a few and back them up just in case.

Do not make any changes to the profile folder(s).

> So, if everything goes right when I install the new download I will eventually want to delete/uninstall OLD Firefox. So, do I click on the "uninstall" folder and will it delete everything or will I need to actually "delete" the folder "after" I've successfully installed the new download. Will the "uninstall" option work properly with the folder it's in has been renamed to "Old Firefox" ??

Don't run the uninstall, it doesn't notice renamed folders and will uninstall the live installation. Just delete the Old Firefox folder when you no longer want it.

Hi Again jscher2000, I'm pretty sure I did something wrong !! I renamed C:\program files\mozilla firefox to C:\program files\ oldmozilla firefox Then I downloaded and installed the "new" update firefox install file. It did install firefox, but just a totally naked browser with no book marks, tool bars, etc.. After "re"reading your reply above, I think I renamed the wrong folder to old. So, at least "everything" is still there (I hope) !! I probably should have gone "one" more step down the folder trail to put the "rename" old on; but I don't know which folder to do. There's a "browser" folder, but I'm not sure what to do. I need advise on how to back out of where I'm at now and "re" do the right way. So, please give me more "specific" instructions on where to go from here. If I remove the "old" from the rename that should allow that "total" folder to be available again. Then rename whatever folder you tell me to do to "old" and then download the install file again ?? This exercise is really getting more crazy and I hope I can get things back right again ?? BTW, after I installed the download file and found things where not right, I looked in explorer to see the folders. There was "not" a "new" mozilla\firefox folder and above the folder renamed "old" mozilla\firefox was a folder named mozilla maintenance service dated today. And, when I clicked on "install" for the downloaded program, it said it was putting the install in a "Users" folder. Again, I just hope everything is "saved" in the "oldmozilla firefox folder. Thanks in advance, Don

Hi Don, hold off on renaming or removing anything.

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 one profile 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.

Does your wife's tablet have any other profile(s) listed on this page? If so, you can check whether it is the one she was using recently 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.

Any luck there?

Note that Firefox may have locked the original profile if it thinks that you have used this profile with another Firefox installation.

• https://support.mozilla.org/en-US/kb/dedicated-profiles-firefox-installation
• https://support.mozilla.org/en-US/kb/understanding-depth-profile-installation

Hi jscher, Well, I tried your last solution and it worked great. Sorry it took me so long to get back but we had out of town company and I've just now gotten the chance to get back to this issue. I can now sign on to FF with my wife's tablet and it boots up to the proper page with all the old settings which is great but I still have a few questions:

1.When I first downloaded the new FF update and installed it, it created a new short cut on the desktop. When I looked at where the URL in the new short cut was it was my "re" named "old" mozilla firefox folder. I was originally told that when renaming the folder to "old" would cause the new download to make a "new" mozilla firefox folder. But, it appears that the renamed "old" folder is still in use so does that mean I will "leave" the "old" renamed folder alone and installed ??

2. When I use the method for FF updates of clicking on "help", then "about" and then "update", will it still function properly as before ?? If not, what is the "new" method for updating ??

3. Do I just leave the new folder created with the new install of "mozilla maintenance service" and what is it's function ??

4. Since there were many steps in the solutions for this issue listed on this support page which one do I click on to give you credit for this solution and will it show "all" of the steps to get there for any other people looking for this fix ??

 Thanks so much for sticking with me on this solution.  It was a very heavy load on my brain for a while which is now finally gone..

It sounds like the new profile was the most important element.

To create a desktop shortcut for the installation in the regular folder:

Open C:\Program Files\Mozilla Firefox

Right-click firefox.exe

Choose Send to > Desktop (create shortcut)

It's possible Windows will add (1) to the name to avoid a duplicate shortcut name. Whether it's that or something else, there should be a way to distinguish it from the old one.

Hi jscher, I'm back again (ha), When I last wrote to you I didn't get an answer to the number 2 question as follows:

2. When I use the method for FF updates of clicking on "help", then "about" and then "update", will it still function properly as before ?? If not, what is the "new" method for updating ??

 Well, there's a new release of FF out now of 115.0, so I tried to used our "regular" method of updating as spelled out above and when I clicked on the "about" option it started "trying" to download the 115.0 update but it never

happened; it was just stuck in a loop. I think it might have been looking for the "original" FF that I think is still loaded on the tablet ?? Anyway, I had a heck of a time stopping the loop as I couldn't close FF. I had to restart (reboot) the tablet and then delete the icon in the activity tray. So, now the main question is "how" do I install update on the tablet ?? Please see a paste of question 3 from above:

3. Do I just leave the new folder created with the new install of "mozilla maintenance service" and what is it's function ??

In this folder I see a file called "updater". I don't want to click on it as I don't want to do anymore harm if it's not what I need to do. If this file will download updates and install them that would solve my problem.

 Other than this update issue, the tablet is working great using FF, so I hope I can have a way to update.  Thanks, Don

Regarding #2, I don't know why that didn't work. You could try again in a couple days.

Assuming your Firefox was installed from Mozilla and not from the Windows store, the other option is to download the full installer and run that -- it will detect your installation of Firefox and replace it:

https://www.mozilla.org/en-US/firefox/all/#product-desktop-release

Regarding #3, the Mozilla Maintenance Service is related to the checkbox on the settings page: "Use a background service to install updates". (I think this was a way to bypass the annoying Windows dialog to allow changes to your computer that we always saw starting back in the Windows Vista/Windows 7 days.) Whether you use that or not, I don't think it makes sense to delete this folder since it will be reestablished after the next update.