From your old data tape backup, restore the EDB files consisting of your original mailboxes on your Exchange 2000 to any available space even on a file server. I would purchase Ontrack Power Controls or Quest Recovery Manager for Exchange which can open up the edb files directly and then you would be able to extract the information you need to a pst file. Highly recommended tool. Once you have the pst file, you can have the user point to it within Outlook and then upload or use directly.
Alternatively you can set up a recovery envrionment running Exchange 2000, restore the EDB to the recovery server, and then connect to the restored mailbox through Outlook — still in your recovery environment. Then use Outlook to export to PST, transport the PST to your production environment, and merge the detla (or whatever messages are of interest) with the user’s current mailbox.