its spyware. Did u install Wintools?
Wintools acts as a search page and home page hijacker.
Sometimes when u install Gain, Gator or Claria Wintools gets installed also without any message.
Try to remove wintools from add/remove programs
after doing this run adaware or any other spywarekiller
here are some of them: http://www.techist.com/downloads.php
Hope this helps!