Exmerge Exchange 2000
It shouldn't have take me so long to find a copy of Exmerge.exe for E2K online... because it isn't.
http://support.microsoft.com/kb/174197
The Microsoft Exchange Mailbox Merge Program (Exmerge.exe) enables an Exchange Server administrator to extract data from mailboxes on an Exchange Server computer and then merge this data into the same mailboxes on another computer that is running Exchange Server. The Exchange Server 4.0, 5.0, and 5.5 version of this program is included in the Microsoft BackOffice Resource Kit, Second Edition. The Exchange 2000 Server version of Exmerge is included on the Exchange 2000 Server CD in the SupportUtilsI386Exmerge folder.