Search hijacked

I have recently become a victim of a hijacked search. I am able to surf the net okay, but every time I try to search something I get redirected to other search sites or advertisements. I have downloaded hijackthis but don't know enough to fix the problem. Can anyone help. Thanks.

Take a read through this and then start a fresh thread in this forum and post accordingly. Please don't forget to include a brief description of your problem, and somebody will be along as soon as.
Helpers look for posts with zero replies which is why you need to start afresh and why i'll lock this one.