My homepage in Windows XP has been hijacked by a search engine and no matter what I change it to when I reboot the pc and open explorer again it reverts to this unwanted search engine. I am also unable to find the programme in the hard drive.
Something similar happened to me once. I had to use system restore, in the system tools menu to get it back to normal. Choose a restore point from before the first time you noticed it, and it might revert back.