OL2000 does NOT HAVE AUTOCOMPLETION! Sorry, but this question comes up
about 5X a day I think. Anyway, OL2000 uses Autoresolution. It attempts to
find matches in your contact folder based on the keystrokes that you type
into the To: field. Make certain that all contact folders are properly
configured to work with your e-mail.
Autocompletion came about in XP and 2003 versions of OL.