Try this: *Download the Firefox installer and save the file to the desktop<br>https://www.mozilla.org/en-US/firefox/all/ *Start the installation with a double-click on the desktop icon You may have to disable your security software temporarily or boot the computer in Windows Safe Mode with network support (press F8 on the boot screen)if you keep having problems. *http://www.bleepingcomputer.com/tutorials/how-to-start-windows-in-safe-mode/