If its a kind of an adware search engine then the best thing is to re-install the firefox and when it asks you do you want to import any data from any where just deny it and if it asks to use the previous data from the browser then also do not let it do that for more answers go to the FaQ for changing the default search engine.

Reset Firefox {web link} is a LAST RESORT ! !

Bookmark and use this; Download the Mozilla Search Reset {web link} This add-on is very simple: on installation, it backs up and then resets your search preferences and home page to their default values, and then uninstalls itself. This affects the search bar, URL bar searches, and the home page.

Sometimes a problem with Firefox may be a result of malware installed on your computer, that you may not be aware of.

You can try these free programs to scan for malware, which work with your existing antivirus software:

• Microsoft Safety Scanner
• MalwareBytes' Anti-Malware
• Anti-Rootkit Utility - TDSSKiller
• AdwCleaner (for more info, see this alternate AdwCleaner download page)
• Hitman Pro
• ESET Online Scanner

Microsoft Security Essentials is a good permanent antivirus for Windows 7/Vista/XP if you don't already have one.

Further information can be found in the Troubleshoot Firefox issues caused by malware article.

Did this fix your problems? Please report back to us!

pkgslg said

While going to options and clicking search tab, I change the default search engine but on restart again the earlier search engine appears as default search engine. I donot find any option to permanently remove the search engine. Only the option of select/deselect is there. Please advise.

I did use "Reset Firefox" and it did solve my problem very easily. It was wonderful experience to see the irritating problem go away in a moment. Thanks a lot.

Glad to help.

It’s very sad, but many of the software down-loaders / installers will trick you into installing not only their program, but other programs as well. You have heard of the fine print in shady contracts, right? Well, some installers you need to look at the itsy bitsy teeny weeny fine print. You are thinking you are giving the installer permission to install the program you want by using the recommended option. But if you use the Manual Option Instead, you discover all kinds of stuff that you do not even know what it is or what it does. From now on, everyone needs to Use The Manual Option to put a stop to this.