Delete the Firefox installation folder, which is located in one of these locations, by default:.
After the download finishes, close all Firefox windows (click Exit from the Firefox or File menu).
Download the latest Desktop version of Firefox from and save the setup file to your computer.
Note: You might want to print these steps or view them in another browser. This means you remove Firefox program files and then reinstall Firefox. Certain Firefox problems can be solved by performing a Clean reinstall.