Outlook power users know that the F11 key sends focus to the Find a Contact drop-down list in the Toolbar. The names shown in this are stored in the registry and, for Office 11, can be cleared by deleting this key from the registry:

HKEY_CURRENT_USER\\Software\\Microsoft\\Office\\11.0\\Outlook\\Contact\\QuickFindMRU

Power users of earlier versions of earlier versions of Office should see that the number 11.0 shown in the path above can be changed to a lower number to accomplish the same task. So users of Office XP can go here:

HKEY_CURRENT_USER\\Software\\Microsoft\\Office\\10.0\\Outlook\\Contact\\QuickFindMRU