Sometimes junk carries over in Firefox's program folder. If you uninstalled, that usually would cure that, but just in case... we generally suggest:

Clean Reinstall

We use this name, but it's not about removing your settings, it's about making sure the program files are clean (no inconsistent or alien code files). As described below, this process does not disturb your existing settings. Do NOT uninstall Firefox, that's not needed.

It only take a few minutes.

(A) Download a fresh installer for Firefox 47.0.1 from https://www.mozilla.org/firefox/all/ to a convenient location. (Scroll down to your preferred language.) For maximum plugin compatibility, choose the 32-bit version.

(B) Exit out of Firefox (if applicable).

(C) Using Windows Explorer/My Computer, rename the program folder as follows:

C:\Program Files (x86)\Mozilla Firefox

to

C:\Program Files (x86)\OldFirefox

(D) Run the installer you downloaded in step (A). It should automatically connect to your existing settings.

Note: Some plugins may exist only in that OldFirefox folder. If something essential is missing, look in these folders:

• \OldFirefox\Plugins
• \OldFirefox\browser\plugins

Any improvement?

When I research this error in old threads, I often see a recommendation to check your Windows system files for possible damage. This Microsoft article describes the SFC tool (System File Checker) to do that:

https://support.microsoft.com/en-us/kb/929833

I will just add one more possible solution. Go to the folder where you have currently installed firefox. Right-Click on firefox.exe file. Go to Properties. Now, under the Compatibility tab check run as administrator. Also, under Security tab for Administrators make sure proper permissions are given.

You should never set Firefox to run as administrator as that will cause serious security issues.

Did you do a clean reinstall and have deleted the Firefox program folder?

Boot the computer in Windows Safe mode with network support to see if that has effect in case security software is causing problems.

• http://www.bleepingcomputer.com/tutorials/how-to-start-windows-in-safe-mode/
• http://www.7tutorials.com/4-ways-boot-safe-mode-windows-10

Thank you all for your FAST response, however, I'm still stuck on this first step from jscher 2000. jscher 2000: I followed the directions in your 2nd email to clean the Windows system files.They were fine. Now I am doing the steps from your first email, but am having a hard time on step (C)as I don't know how to use the Windows Explorer/My Computer to find anything that looks like what you have below; meaning C:\Program Files (x86)\Mozilla Firefox. Can you tell me how to do this step? (C) Using Windows Explorer/My Computer, rename the program folder as follows:C:\Program Files (x86)\Mozilla Firefox toC:\Program Files (x86)\OldFirefox

Thanks so much.Diane

Windows Explorer is the file manager of Windows. There's often an icon for it on the desktop or the Start menu. Two other ways to open it are:

• Hold down the Windows key on the keyboard and tap E
• In the Start menu search box, type explore and watch for Windows Explorer to come up on the results list, then click it to run it

Once Windows Explorer starts, look for Computer and under that should be the C drive, or in the address bar at the top of the program, click in a blank area, press Backspace to clear what's there, and type c:\ and press Enter to load it.

That should list a bunch of files and folders. Look for Program Files (x86) and double-click into that folder.

Find Mozilla Firefox here, right-click it, choose Rename, and then you can edit it to OldFirefox.

Success?

Thank you, thank you! jscher 2000 - I got it!!!!! Yea! It took a while as it wasn't letting me change the file name as it kept saying I had a file open. So I restarted the computer and it took! It did a compatibility check on its' own, so I didn't need to do what cor-el suggested. (Plus I didn't know how to do a Safe mode start without it suggesting it.)

Thanks to everyone for your help...I finally got my Firefox back...I missed it terribly! Yeah!!!! Diane

Oh and jscher2000, thanks for the additional help on changing the file name; I had never done that before. Plus, I needed the info about the backspace because it didn't give me the drop down info with the programs. Thanks again! Diane