Make some room if the free space on the hard drive is low. You can move files to an external drive.

• 1 Download Firefox Full Installer For All languages And Systemsv39 {web link}
• 2 Uninstall Firefox from your computer {web link}
  DO NOT remove your profiles.
• 3 After, reboot the computer. Then run the full installer.

Thanks, Fred. I have a few follow-up Qs:

- Can I uninstall Firefox first? That would insure enough space. - Will I be prompted by the uninstall regarding removing profiles? If not, how do I do what you cautioned about (DO NOT remove...)? - Finally, I am concerned about IE reputation for viruses - it is safe to use for the Firefox download?

OneEyeOpen said

- Can I uninstall Firefox first? That would insure enough space. - Will I be prompted by the uninstall regarding removing profiles?

If there is a problem with any program where you decide to do a re-install, it is recommended that the old program be removed. This is in case of corrupt or missing files.

Many programs can leave or remove old settings during removal. If you plan to reinstall something, keep it's settings. Note: sometimes it's something in the settings that is the problem. If after, there is still a problem, remove / delete the old settings.

- Finally, I am concerned about IE reputation for viruses - it is safe to use for the Firefox download?

All programs are vulnerable to virus attack. That is why we use anti-virus and mal-ware scanners. Further information can be found in the Troubleshoot Firefox issues caused by malware article.

Run most or all of the listed malware scanners. Each works differently. If one program misses something, another may pick it up.