• 1 Download Firefox Full Installer For All languages And Systemsv41 {web link}
• 2 Uninstall Firefox from your computer {web link}
  DO NOT remove your profiles.
• 3 After, reboot the computer. Then run the full installer.

Ok Fred. 1. I have downloaded that Full Installer many times now. In the downloads folder it calls itself Firefox Setup 41.0.1 exe - is that correct? 2. I have uninstalled (again), but what do you mean about profiles? The only one I have is the original profile that I moved to the desktop. Are you suggesting I put this one back in Appdata/Roaming/Mozilla? I need to be sure what to do about this (old) profile before rebooting and running the installer again.

OK I have done all the steps without bringing back my old profile. At this point Firefox has worked, but of course I have lost all my history, recent sessions and bookmarks. Before I shut down and restart Windows, which previously cause problems, should I take advantage of this totally fresh install by running any diagnostics?

If not the next step is to shut and restart and see if Fiefoxcontinues to work.

The final step, if above goes okay, would be to reintroduce the couple of important files from the old profile (as listed by you earlier). Do you agree with this course of action?

First, the profile you moved to the desktop; leave this here, unchanged. When needed, Copy files to another profile. This way, you will still have a "clean" copy in case of problems.

https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles Use these instructions to create a new, blank profile. Then use it as is. Make no changes at this time. Does it work?

If there is no problem, then you can Copy files from the desktop to it.

Transfer User Profile Files

I take it the new profile is working without problem, yes? When you are ready, we can start moving parts of your old data and Copy it to the new profile.

First; open your file browser to the New profile;

Type about:support in the address bar and press enter.

Under the page logo on the left side you will see Application Basics. Under this find Profile Folder. To it’s right press the button Show Folder. This will open your file browser to the current Firefox profile. Now Close Firefox.

Second, open the file browser to the Old profile. You should see it on the directory "tree" in the first file browser. Right click on that folder and select Open In New Window.

Warning ! ! Only Copy the files you are told. We will avoid anything that might be the cause of your problems. Here is the list of files;

cookies: Do not bother. Cookies will be created when you return to the web site. However, you will have to log in everywhere.

extensions(add-ons): it would be better to download them fresh.

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key3.db and logins.json: These are the Password files.

persdict.dat: custom dictionary – words you added to the dictionary

mimeTypes.rdf: What to do with what type of file.

places.sqlite: History and Bookmarks.

prefs.js: Your settings. Note, this may be contaminated.

Copy these files from the old to the new. You will get a message about the files already exist. Choose to over-write for each file.