Try this:

1. Click on the Windows start button in the bottom-left.
2. In the search field, type C:\Program Files\Mozilla Firefox
3. Click on the Mozilla Firefox folder that appears in the results. That should show you the folders and files in the C:\Program Files\Mozilla Firefox folder.
4. Right-click on the file firefox.exe.moz-upgrade and delete it.

NOTE: If you're using 64-bit system, the text to type in step 2 is C:\Program Files (x86)\Mozilla Firefox

If files already have been downloaded then remove the files in the updates and updates\0 folder.

You can also delete active-update.xml and possibly updates.xml (this will clear the update history).

• http://kb.mozillazine.org/Updates_reported_when_running_newest_version
• http://kb.mozillazine.org/Software_Update (Software Update not working properly)

C:\Users\<user>\AppData\Local\Mozilla\Firefox\Mozilla Firefox\updates
(%LOCALAPPDATA%\Mozilla\Firefox\Mozilla Firefox)

there is no firefox.exe.moz-upgrade file there is one that is firefox.exe.mox-delete though, there is nothing that has active-update.xml

Try deleting firefox.exe.moz-delete.

Another method:

1. Uninstall Firefox using the control panel.
2. Reboot your computer.
3. Delete the entire C:\Program Files\Mozilla Firefox folder.
4. Install the latest version from http://www.mozilla.org/firefox/

Worked thank you!