I do not specifically recognise that one but have a look at

• Remove a toolbar that has taken over your Firefox search or home page
• What to do when searches take you to the wrong search website

You are likely to have to find and uninstall the unwanted software and then reset whatever has been changed. As mentioned above there is an add-on that will help with that.

Note also the reset option, but read the notes about what will be lost. You may wish to bookmark open tabs, and extension's homesites before ressetting if you try that.

This is malware. You might have to use some sort of malware or adware remover. I would suggest microsoft security essentials.

Also if you are looking for a good free youtube downloader I would suggest DVDvideosoft. Google that and you will have everything you need. download videos, mp3's, convert video and audio.. anything. Completely freeware. I have used it for 4 years now.

You can check for problems with preferences and try to rename or delete the prefs.js file and possible numbered prefs-##.js files and a possible user.js file to reset all prefs to the default values.

• http://kb.mozillazine.org/Preferences_not_saved
• http://kb.mozillazine.org/Resetting_preferences

• https://support.mozilla.org/kb/Preferences+are+not+saved
• https://support.mozilla.org/kb/Resetting+preferences