#Go to [http://www.mozilla.com/en-US/firefox/all-older.html Download Firefox v3.6.17] and download it to the desktop.<br><br> #Then go to Add/Remove Programs, scroll down to "Mozilla Firefox" and remove it, choosing to keep your bookmarks, customizations etc., (don't checkmark the box).<br><br> #Then reboot and delete the folder called "Mozilla Firefox" at this location: C:\Program Files\Mozilla Firefox<br><br> #Finally run the installation file you downloaded to the desktop earlier.<br><br> Your bookmarks, customizations etc., are maintained in a different location and will become available to you again once you complete the installation.<br><br> ---- After you complete the installation, go to the [http://www.mozilla.com/en-US/plugincheck/ Plugins Check] page and update those where necessary.