If you're using Internet Explorer:
Click the Tools menu and then Internet Options.
Within the Internet Options window, click the content tab.
Click the Autocomplete button.
Within this window you can click Clear forms to clear all form data except for passwords and click Clear Passwords to clear the passwords.
In addition to clearing these fields, if you do not want Internet Explorer to save this data in the future, you can uncheck any of the available boxes in this window.