Note that it is a little out-of-date; I recommend using Windows 2000 SP2, plus the latest hotfixes and updates.
Once you've verified that your cluster is running as expected and tested failover, take a backup of the standalone Exchange 2000 server containing the mailboxes. After the backup has completed, move the mailboxes (using Active Directory Users and Computers) from the un-clustered server to the EVS in the cluster. Once that is complete, re-home any public folders and any other services/components.
Once you have verified everything is working properly for your users, uninstall Exchange 2000 from the standalone server, and remove it from Active Directory.
Hope this helps.
This was first published in October 2001