The fourth section in the Delete Browsing History window deals with Form data. Anytime you enter information into a form on a website, Internet Explorer stores some of that data. For example, you may have noticed when filling out your name in a form that after typing the first letter or two your entire name becomes populated in the field. This is because IE has stored your name from entry in a previous form. Although this can be very convenient, it can also become an obvious privacy issue.
To remove this stored data from your hard drive, click on the button labeled Delete forms.... A message dialog will then appear asking Are you sure you want to delete previously saved form data? Click on the Yes button. All saved information that you had previously typed into web forms is now permanently removed.