Having IE "remember" the last thing i entered into a textbox control with the same ID is very handy -particuarly for doing research with search engines and wanting to know what you have already tried. Unfortunately when doing demo's you really don't want to give way that you have either done that sample before or what you will be typing....
Well Emily Waghorne pointed out this is easily over come by dropping down the textbox history selecting the previous attempts and hitting delete!
Matthew Cosier also pointed out you can do this for all forms via:
tools -> internet options -> content -> auto complete… clear forms/clear passwords