Do a clean (re)install:

• Download a fresh Firefox copy from http://www.mozilla.com/firefox/all.html and save the file to the desktop.
• Uninstall your current Firefox version and remove the Firefox program folder before installing that copy of the Firefox installer.
• Don't remove personal data when uninstalling.
• It is important to delete the Firefox program folder to remove all the files and make sure that there are no problems with files that were leftover after uninstalling.

Thanks cor-el for the above. However no improvement on the original problem. I uninstalled as suggested, then used Windows 7 search facility to confirm there were no Mozilla folders left, before installing the new version.

The error message seems to indicate there is a file or reference left somewhere on the system. Any other suggestions.

Regards Bob

You can try to reboot after removing the folder and verify that they are gone and that not some files were restored by security software.

You can check if there is a VirtualStore folder with leftover files.

C:\Users\<user>\AppData\Local\VirtualStore\Program Files\Mozilla Firefox\
C:\Program Files\Mozilla Firefox\

Cor-el

Have tried your suggestions but same result. The only Mozilla files that I can find left on my system is my profile, cache & offline cache files under "User". Not sure where my bookmarks are filed.

Try a custom install in a different program folder like "C:\Program Files\Mozilla Firefox36\"

Cor-el

Before I tried your suggestion re putting Mozilla in a different folder ( I needed a break!!), a friend using her guest account (Standard privileges), logged onto the Mozilla icon on her start up page and it works with no problems. However, whenever I use the Mozilla Icon from my start up page (Administrative privileges) it comes up with the mentioned error message and won't work. I have deleted my Mozilla icon several times, sending a new one from the application to the desk top but with the same result.

Any suggestions - regards Genesis2

Try to run Firefox once as Administrator (right-click context menu: Run as Administrator) to get elevated privileges.

You can also check for files in the VirtualStore folder.

C:\Users\<user>\AppData\Local\VirtualStore\Program Files\Mozilla Firefox\updates

(AppData is a hidden folder)

It now works each time if I run it as Administrator as detailed in your previous reply - however as I normally operate with full Administrator privileges, I am unsure why only this approach works. If I don't right click and run as Administrator, it still won't operate and with the same original error message.

I couldn't find any Mozilla files in the VirtualStore folder.

Many thanks