You are troubleshooting a stand-alone computer problem. The client states that he was browsing the Internet. After clicking on a link, he found that his browser performance became very slow. Also, a small window opened telling him to click "Yes" for help. The user clicked on the Yes button. Now every time he opens his browser, he is redirected to a web site that sells PC troubleshooting software. What step should you take first to resolve this problem?