Get the full installer from Download Firefox For All languages And Systems {web link}

Hi Fred. Thanks for your reply. I've tried what you suggested but I still got 'the system cannot find the file specified'. Thanks anyway. Nell126.

Firefox is packed as a 7-ZIP archive. If there is a problem with unpacking this archive then you get this error.

It is possible that (anti-virus) security software is causing the problem. Try to disable security software temporarily to see if that makes a difference.

Try this:

• download the Firefox installer and save the file to the desktop
  *https://www.mozilla.org/en-US/firefox/all/
• start the installation with a double-click on the desktop icon

If you keep having problems then boot the computer in Windows Safe mode with network support to see if that works better.

• http://www.bleepingcomputer.com/tutorials/how-to-start-windows-in-safe-mode/
• http://www.7tutorials.com/4-ways-boot-safe-mode-windows-10