I had a client recently who run running a windows XP Pro laptop. This client needed to change windows domains. In this process a new windows user profile was created.
After setting up Outlook the user then tried to send email to friends on his contact list. The user used to be able to type a few letters and the rest of the email address would appear in a list. This is what is called Outlook Autofill.

When a new user profile is created the outlook autofill cache file is empty. In the case of only a few contacts it may not be a big problem however this user had over 300 contacts that were already in the previous cache file.

Long story short I needed to copy the old cache file to the new profile.

On Windows XP the file is located at:

c:documents and settingsusernameapplication datamicrosoftoutlookOutlook.nk2

You must close Outlook if it is running and then copy the file from the old profile to the new profiles folder.

After Outlook is restarted the autofill cache should have all of the previously entered email addresses available in the drop down list.

Hope this helps somebody else.

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