After clicking on the Delete all... button, a message dialog appears asking Are you sure you want to delete all Internet Explorer browsing history?
Located directly under this question is an optional checkbox labeled Also delete files and settings stored by add-ons. Some browser add-ons and plug-ins may store similar information to Internet Explorer itself, such as form data and login passwords. If you wish to delete this information as well, click on the checkbox to activate this option.
Finally, click on the Yes button to delete all of your Internet Explorer browsing history information.