As you browse the internet, Windows keeps track of everything that you type into forms.  This information is put in the registry.  In order to edit the AutoComplete list click on the Edit AutoComplete button.  This will open your browser and put a form in it.  There are instructions at the top of the form.  Basically what you need to do is go through each textbox and check the words in the popup.  To get the popup to show, put the cursor in the textbox and press the Down key.  If you want to delete an item, select it and press the Delete key.  If all items in a textbox are deleted, that textbox will also be removed from the AutoComplete list.