Here is a great little utility Aaron Silber sent me that is super focused and super useful. I have had the same misspelled email address popping up with for a particular friend for the LONGEST time and have now FINALLY been able to delete it! :) Here is Aaron’s email below.
I just came across this wonderful utility which everyone seems to always be looking for, NK2Edit. Yup, you guessed it, a single executable, no installation, completely freeware program which will allow complete control over your AutoComplete list in Outlook. I believe it even supports Outlook 2010.
You can download it from here: http://www.nirsoft.net/utils/outlook_nk2_edit.html