I don't know if this is common knowledge but something I just found may be helpful.

To delete individual autocomplete entries without deleting the history..

Start / Run type in 'regedit' press 'enter'

H_Key Current Users / Software / Microsoft / Internet Explorer / Typed Urls

and in the right hand pane the urls in the drop down autocomplete box will appear, highlight them and deltete, reboot and hey presto your boss can't find out you've been looking at pictures of model electric train sets.