Do a clean reinstall and delete the Firefox program folder before (re)installing a fresh copy of the current Firefox release.

Download a fresh Firefox copy and save the file to the desktop.

• Firefox 21.0.x: http://www.mozilla.org/en-US/firefox/all.html

Uninstall your current Firefox version, if possible, to cleanup the Windows registry and settings in security software.

• Do NOT remove personal data when you uninstall your current Firefox version, because all profile folders will be removed and you will lose all personal data like bookmarks and passwords from profiles of other Firefox versions.

Remove the Firefox program folder before installing that newly downloaded copy of the Firefox installer.

• (32 bit Windows) "C:\Program Files\Mozilla Firefox\"
• (64 bit Windows) "C:\Program Files (x86)\Mozilla Firefox\"

• It is important to delete the Firefox program folder to remove all the files and make sure that there are no problems with files that were leftover after uninstalling.
• http://kb.mozillazine.org/Uninstalling_Firefox

Your bookmarks and other personal data are stored in the Firefox profile folder and won't be affected by an uninstall and (re)install, but make sure that "remove personal data" is NOT selected when you uninstall Firefox.

If you keep having problems then also create a new profile.

• http://kb.mozillazine.org/Profile_folder_-_Firefox
• http://kb.mozillazine.org/Profile_backup

• http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Clean_reinstall

It is because you might have downloaded the optimised version of Mozilla Firefox made for Yahoo! Do a fresh reinstallation of Mozilla firefox's appropriate version. You can download it from here: Firefox 21.0.x: http://www.mozilla.org/en-US/firefox/all.html

And yes if you have an add-on of Yahoo search toolbar then you can disable it from the firefox installation toolbars.

Remember do not download the optimised version made for yahoo. As it will only have that yahoo search home page! Thank You!

Thank you very much! You folks are gracious to help out the inept such as myself!!!

IN FRENCH : J'ai trouvé un truc qui fonctionne enfin. Sur Mac, mais cela doit être la même logique sous d'autres OS. Localiser le fameux fichier yahoo.xml qui se cache dans une bibliothèque "searchplugins"... et NE PAS SEULEMENT LE SUPPRIMER (il reviendrait), mais après sa suppression, y créer un dossier vide qui porte le même nom. Le fichier ne sera alors plus actif, et plus recréé !

IN +/- US : Locate the file yahoo.xml' in a "searchplugins" in your Library folder. Put it in the trash AND create, at the same place, an empty folder with the same name. It works on Mac... and certainly with other OS !

It amazes me that firefox would allow a virus like yahoo to install things at will. And to top it off it doesn't try to stop it....???