It is best you not mess with the registry (also, don't use CCleaner, it has been known to break many things and was used to spread a virus not too long ago).

The registry is best not messed with except to follow very specific troubleshooting steps. Without knowing what keys you are talking about, or if they are causing a problem, I suggest leaving them.

Question, was there a reason you uninstalled Firefox? I'd love to help you fix that issue so you can re-install it and continue using it.

[Incorrect information removed by Admin]

Note : Firefox 56.0.2 is current release https://www.mozilla.org/firefox/all/ Full Version Installer Note : Firefox 57 Quantum release date Nov 14th https://www.mozilla.org/en-US/firefox/quantum/ Note : Legacy Extensions will be disabled and or removed.

Please let us know if this solved your issue or if need further assistance.

The Boss speaks.

Ok if having OS issues try this to fix things up.

Repair System Registry and Files

(FOR DOING Above & Below - WINDOWS All OTHER VERSIONS - Use Search To Find Command Prompt ** Enter CMD.exe to Find COMMAND PROMPT Then Right Click & RUN AS ADMIN)

To run the SFC command use the Windows key + X keyboard shortcut to open the Power User menu and select Command Prompt (Admin). Type "SFC /SCANNOW" (without quotes or copy/paste) and press Enter. For more information on using SFC, please refer to the Microsoft KB: Use the System File Checker tool to repair missing or corrupted system files

Run the Windows Deployment Image Servicing and Management (DISM) and System File Checker (SFC) tools as Administrator. The DISM and SFC tools scan the integrity of the Windows image and all protected system files replaces corrupted, damaged and incorrect versions. (FOR DOING Above & Below - WINDOWS All OTHER VERSIONS - Use Search To Find Command Prompt ** Enter CMD.exe to Find COMMAND PROMPT Then Right Click & RUN AS ADMIN)

Windows 10 To run the DISM command use the Windows key + X keyboard shortcut to open the Power User menu, then select Command Prompt (Admin). Type "DISM /Online /Cleanup-Image /RestoreHealth" (without quotes or copy/paste) and press Enter. While running DISM you may notice the process will appear to pause at 20%. After a few minutes the operation will continue.

Note : SFC uses files found locally on your system Note : DISM goes up to Microsoft for the files.

Please let us know if this solved your issue or if need further assistance.

There are some references to Mozilla in the registry that are used by other programs. For example, if you install Flash, it will add information about the Flash plugin under a MozillaPlugins key. These keys might be read by other browsers that are plugin-compatible with Firefox, so I suggest not removing them.