Start Firefox in Safe Mode {web link} by holding down the <Shift> (Mac=Options) key, and then starting Firefox.

A small dialog should appear. Click Start In Safe Mode (not Refresh). Is the problem still there?

The problem persists in the same way when Firefox is started in safe mode.

Let’s do a full clean re-install;

Download Firefox For All languages And Systems {web link}

Save the file. Then Close Firefox.

Using your file browser, open the Programs Folder on your computer.

Windows: C:\Program Files C:\Program Files (x86)

Mac: Open the "Applications" folder. https://support.mozilla.org/en-US/kb/how-download-and-install-firefox-mac

Linux: Check your user manual. If you installed Firefox with the distro-based package manager, you should use the same way to uninstall it. See Install Firefox on Linux; https://support.mozilla.org/en-US/kb/install-firefox-linux

If you downloaded and installed the binary package from the Firefox download page, simply remove the folder Firefox in your home directory. http://www.mozilla.org/firefox#desktop ++++++++++++++++++++++++++++ Do Not remove the profiles folder.

Look for, and rename any Mozilla or Firefox program folders by adding .old to them. Do not rename the Mozilla Thunderbird folder if there is one.

After rebooting the computer, run a registry scanner if you have one. Then run the installer. If all goes well, remove the OLD folders when you are done. +++++++++++++++++++++++++++ If there is a problem, start your Computer in safe mode and try again.

http://encyclopedia2.thefreedictionary.com/Linux+Safe+Mode This shows how to Start all Computers in Safe Mode; Free Online Encyclopedia

These are all good suggestions and I followed them. However the problem persists.

I do believe that this is a WIndows 10 problem and not a Firefox problem because I have other programs that are supposed to be able to open folders from a list that used to work but now result in the same error. I think it's possible a recent Windows update borked this functionality.

I only posted in case other users had complained about the same behavior and someone knowledgeable was familiar with it.

I don't expect the solution that was provided to me to fix a search utility, "Search Everything" will apply to Firefox but I know there are ways to tweak FF that are not obvious to the normal user.

This is what fixed my similar problem with Search Everything:

There might be a workaround for the specific case of Everything: Instead of relying on the registry to form the connection between Everything and Explorer.exe, you could start Explorer.exe straightaway, taking the "outside route":

Under Menu:Tools > Options > Context Menu change the following: OPen (Folders) : Command = $exec("%SystemRoot%\explorer.exe" /n,/e,"%1") Open Path : Command = $exec("%SystemRoot%\explorer.exe" /n,/e,"%1\..")

That way you just tell the shell to start Explorer.exe (the filemanager) and open in the selected folder.

Perform a System File Check to fix corrupted system files

Win 7, 8, 10, Vista: https://support.microsoft.com/en-us/kb/929833 Win XP: https://www.microsoft.com/resources/documentation/windows/xp/all/proddocs/en-us/system_file_checker.mspx?mfr=true

Wiki - Windows 10 System File Check http://answers.microsoft.com/en-us/windows/wiki/windows_10-update/system-file-check-sfc-scan-and-repair-system-files/bc609315-da1f-4775-812c-695b60477a93

https://support.microsoft.com

http://answers.microsoft.com/en-US/windows/forum/windows_10

Thanks but that doesn't work either. This is an error message that cuts against many programs with many "possible" solutions, none have which have worked.

this file does not have a program associated with it for performing this action - Google Search - https://is.gd/zUa1TR

Did you post at Microsoft?