Below are instructions for how to remove a single recipient from the autocomplete list (.nk2). If you are having problems with a single recipient, you can easily delete one item in the cache. I

n Outlook 2003, from the File menu, choose New and then choose Mail Message

1) Type one or more letters of the recipient name or address; this will automatically show cached entries in a drop-down list.

2) Use the arrow keys on your keyboard to select the entry to be deleted. With the entry highlighted, press the Delete key on the keyboard. (Don't press enter first, press delete with the drop down list still showing) This entry is now removed from your AutoComplete/Nickname cache.