Ideally some malwares and spyware will redirect the search engine.
Please perform the following steps and see if it helps:-
1.) Open "Device Manager" by Start--> Run--> type "devmgmt.msc" (without quotes) and hit Enter.
2.) In Device Manager, click on "View-->Show Hidden Devices".
3.) Please expand all the devices by click on the "Plus" sign. Now try to find "TDSSserv.sys" right click Disable.
Note: Do not select Uninstall otherwise the infection will reappear once the computer is restarted.
4.) Reboot the pc.
5.) Now scan your machine with following applications:
> SPYWARE BLASTER
> AD-AWARE PERSONAL
> SPYBOT S&D
6.) Disable and unistall all the addons in your browser.
> If you aer using IE you can unistall addons in Tools-> Manage addons.
7.) Now reset the browser which you are using.
> If you are using IE then it is by Click on Tools->Internet Options. In "Advanced options" tab, under "Reset Internet Explorer settings", Click "Reset.."
8.) Once you are done with everything, clean all the temporary files and cookies from C:/ drive of your machine using CCleaner., and reboot your machine.
Now check your in machine if the issue is resolved.
Please let us know if the above steps were helpful for you. If the issue is stilll persisting please reply back at your convinence.
Thabnk you :)