How to get rid of the ask search toolbar

My home page has been hijacked by Ask search toolbar browser hijack. How did i get this google redirect virus? Every time I open a new tab some Ask search toolbar comes up. It’s really annoying. Another victim said:” My search engine has been attacked by Ask search toolbar, someone give me a removal guide link here, But it requires to download sth, so can someone know whether it is reliable? , and my OS is windows 7, Please help!and i don’t know how to get rid of it? What do you do then?