- Uninstall Firefox (Programs and Features)
Then
Click Start, copy in search [B]%appdata%[/B] Then delete folder Mozilla
Click Start, copy in search [B]%LOCALAPPDATA%[/B] delete folder Mozilla
Then delete following folders:
C:\Program Files (x86)\mozilla firefox
C:\Program Files (x86)\Mozilla Maintenance Service
Restart your PC.
Then install Firefox again.
https://www.mozilla.org/en-US/firefox/new/