Yahoo has removed its old toolbar for Firefox from the internet and now wants you to use your Yahoo bookmarks/favorites on your My Yahoo page. https://downloads.yahoo.com/faqfirefoxtoolbar So... if you are going through all of this just for the Yahoo toolbar, you are heading for disappointment. But meanwhile, where did you download Firefox from? You could try an installer from the following page to see whether it works better: https://www.mozilla.org/firefox/all/ Scroll down to your preferred language. I recommend the regular Windows version rather than the 64-bit Windows version; the 64-bit version doesn't work with most plugins.