It's annoying, isn't it? There are self-help instructions for removal HERE -
and if that doesn't do it for you post back to this topic. But for starters, go to Add/Remove Programs in your Control Panel and look for anything called "Internet Keyword" or "Common Name" and uninstall them. And you'll probably want to post a HijackThis! log in the HijackThis forum. Follow instructions in the pinned post "How to submit a Hijackthis log" HERE.