Please let us know the exact message you see.

You may need to occasionally wait quite a few minutes for fFirefox to shutdown properly, try giving it ten minutes. Then check using Windows task manager and if it has not closed down and should have done use the task manager to kill Firefox before again waiting and then trying to open Firefox. For more information and instructions with screenshots please see:

• "Firefox is already running but is not responding" error - How to fix
• How to run Firefox when your profile is missing or inaccessible

Please post back to say how you get on.

Dear John99, Tank you for your reply to my question about a running Firefox (Ff) and missing Profile. I tested the following. 1) Started the Task Manager (TM). No Ff is running. 2) I double clicked the icon to start Ff. In the meantime the TM is running. 3 A window appears (Title: user account control). This window asks: Do you want to allow this app to make changes to your pc? I click on "yes". (in wondows 7 this question never appeared !) 4) The TM shows the Ff proces with a certain Process ID. Immediately the following message appears: "Firefox is already active, but does not respond. The old (running) Ff should be closed in order to open a new window." Then I press the "close Ff" button. 5 At that moment Ff disappears from the TM list and immediately thereafter a new Ff proces with a new process ID is started. 6) A new message appears on the display with the title: "Missing profile! ". The message content reads: "Your firefox profile cannot be loaded. It is absent or inaccessable." The only choice I have is te click the "OK-button" which I do. 7) The Ff process disappears from my TM list and the screen.

I read somewhere that when one starts Ff, in the profile file a note is made that Ff is running. I don't know if that is true?? If Ff is closed in an inappropriate way this note might be there. But a new question arises because if the new process cannot find the profile file, how will this note ever be deleted?

I looked at the directory where the profile file should be (with all the other files like the bookmark file), but the directory is empty. This makes clear that Ff can't find the file. So I think the problem might be solved when I create a new profile. I can't do that from within Ff because it doesn't start. I have to make a new one without starting Ff. But if the profile directory is really empty it means that my bookmarks are gone too!

The profile directory should reside in C:\users\Kees\%APPDATA%\Mozilla\Firefox\Profiles

A couple of days I (by accident) made the directory Kees (with the properties window) hidden. Might that be the reason that I find an empty directory? In that case, how can I unhide this directory "Kees" and its subdirectories?? I don't know how to do that in Windows 10.

I know it is quite a story, but i like to provide you with as much information as possible. I live in Holland and I am already 70 years old, so I am not familiar with all tricks in Windows 10 yet.

Thank you very much in advance for helping me further. I hop we can solve the problem.

Kind regards, KeesW

First, have you restarted Windows since this problem started? Sometimes after updates Windows starts up with broken permissions for Firefox. You can rule that out by restarting Windows (assuming no new updates are installed this time).

Next, let's locate your profile folder the folder. This is a shortcut

%APPDATA%\Mozilla\Firefox\Profiles

That expands to this:

C:\users\Kees\AppData\Roaming\Mozilla\Firefox\Profiles

It's normal for AppData to be hidden. You can set Windows to show all hidden files and folders: http://windows.microsoft.com/en-us/windows/show-hidden-files

You should find one or more semi-randomly-named folders in Profiles. Anything there?

By the way, it's not normal for Windows to ask about making changes to your computer when Firefox starts up. Could you check to make sure Firefox is NOT set to run as administrator?

To do that, either:

• right-click the Firefox desktop shortcut
• right-click the pinned Firefox taskbar icon, then right-click Mozilla Firefox

In the Properties dialog, click the Compatibility tab and make sure nothing is set/selected on this tab.

Dear jscher2000,

Thank you for your suggestions. The first thing I did was making the Search Window visible on my taskbar. It is not standard visible. Next I clicked with right on the Firefox icon and chose properties and Compatibility. In that window I deselected everything, applied this new setting and closed the window. After starting Firefox the question about running as administrator did not show up anymore. So that problem was solved.

However the other error messages ( Firefox already running and can't acces the profile) remained.

After removing the messages, I typed "map" in the Search Window. A new window named "best match". appeared. I slected "settings" but there was nothing about hidden directories. So I could not deselect anything about hiding directories. At the bottom of this window I found an item "Search my stuff". after clicking that a new window appeared called "map". Two option windows appeared called "Sort:" and "Show:". The firstone showed the text "Most Relevant"and the second showed "Settings". clicking this last one I could choose "Folders", what I did. A new window appeared with another set of possibilities. I chose "Settings". In a small input window I typed 'hidden files'. To my surpise it showed a new window called "search results" and I could click "Show hidden files and folders". Another window appeared named "File Explorer Options". In the part Ädvanced Settings" I now could select "Show hidden files, folders, and drives". After applying this selction my hidden files reappeared again. So the problem of hidden files was solved. I recognized this window from my Windows 7 experience. After closing every window I checked wether my Profiles directory was empty and it was not. All necessary files and bookmark files were there.

Starting up Firefox worked fine and all bookmarks and other stuf was visible again.

Maybe it was not the shortest way of getting to the "File Explorer Options" window", but while stepping through all these kind of windows, I learned again more about Windows 10.

Once more thank you very much for your support and suggestions. Another happy user is walking around on this planet. Have a nice day. Best regards, Kees (from Holland)

Dear Jefferson,

I forgot to tell you that it really seemed to matter that the profile map is NOT hidden. Because after unhiding all the files in C:\users\Kees\........ Firefox worked fine again. Once more thank you and john99 as well for your helpfull suggestions.

KeesW