Please uninstall Firefox. Then Delete the Mozilla Firefox Folders in C:\Program Files and C:\Program Files(x86) and C:\ProgramData Note: your Firefox Profile is saved. But you should make a back up before you do :

• https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles
• https://support.mozilla.org/en-US/kb/export-firefox-bookmarks-to-backup-or-transfer

Reinstall with Current Release Firefox 57.0.4 with a Full Version Installer

• https://www.mozilla.org/firefox/all/

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

Another option: Another user had the same problem. What he did was to install Firefox manually in his computers user folder; C:\Users\Guest

Pkshadow said

Please uninstall Firefox. Then Delete the Mozilla Firefox Folders in C:\Program Files and C:\Program Files(x86) and C:\ProgramData Note: your Firefox Profile is saved. But you should make a back up before you do :

• https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles
• https://support.mozilla.org/en-US/kb/export-firefox-bookmarks-to-backup-or-transfer

Reinstall with Current Release Firefox 57.0.4 with a Full Version Installer

• https://www.mozilla.org/firefox/all/

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

Hi, I did try that, but still got the same problem. Even tried two alternative locations to install - c:\Program Files\Mozilla Firefox\ and c:\Program Files (x86)\Mozilla Firefox\

I haven't tried FredMcD's option yet, but that option is not preferable.

You don't need Admin credits to install as long as your the Owner that is just a valid for install. I think you either set something different in the changes or something corrupted your system to cause the problem. If you removed all traces of FF or Mozilla folder and still get the same problem that would mean you got a Windows sys file error that isn't correctly recognizing the privileges.