It has beeen a while, but try Tools > Options > Preferences tab > Email
Options button > Advanced Email Options button.  The option you are after
should be near the bottom of the dialog.

Outlook 2000 doesn't do auto-complete. It has a feature called
auto-resolution. If you enter part of a name or a nickname then tab out of
the field (or hit Alt-K [Check Names]), Outlook will attempt to resolve the
name against your address book. If it can't it'll red underline it and you
can right click on the name to manually resolve it. Outlook will save the
resolution for future use.

AutoComplete was added in OL2002

Hi PG,

AutoComplete is a feature of Internet Explorer and of Outlook Express.
However, it is not available in Outlook 2000. Outlook 2000 uses a method
called Name Resolution. This feature of Outlook 2000 resolves the name you
are typing or searches through your Contacts list to provide you with the
correct e-mail name. To use this feature, follow these steps: 1. In Outlook
2000, open a new message.
2. Type the first three letters of an e-mail address that is stored in one
of your contacts.
3. On the Tools menu, click Check Name.
You can also use the Check Name toolbar button (the one that has a red check
mark and a picture of a person) or press CTRL+K.

If you have more than one listing of a particular name, the name you type
will have a red wavy line below it. Right-click the name, and then click the
correct name. The next time you compose a message to that person, the name
should resolve successfully, but it will have a dashed underline instead of a
solid underline.

Outlook 2000 dosent have this feature Outlook 2002 have this feture u can
enable this feature in Outlook 2002 by following these steps:-
1. On the Tools menu, click Options.
2. Click E-mail Options, and then click Advanced E-mail Options.
3. Under When sending a message, clear the Suggest names while completing
To, 4. Cc, and Bcc fields check box.

Prem Soni

Hi PG

Autocomplete, where Outlook automatically comes up with email address
options when you start typing an address or name, was not available until
Outlook 2002 and later. Outlook 200 does however have Auto Resolution as
Vince has mentioned but it depends upon the email address being entered as a
contact.