You can do a couple of things.  In the event of a disaster you can
install Exchange in the DRC with the /disasterrecovery switch.  Or,
you can install Exchange in the DRC and keep it off line until
needed.  Then mount the replicated data and re-home the users'
mailboxes.  Here are some articles...

http://www.msexchange.org/tutorials/Recovering-Failed-Exchange-2003-Member-Serve
r-Using-Disaster-Recovery-Switch.html

http://technet.microsoft.com/en-us/library/bb125016(EXCHG.65).aspx

Hope that helps.

David A. Bermingham

Without third party replication software ie. doubletake; xosoft, this
is a manual long process. The only method is to perform the empty
mailbox method (dial tone) on your standby server. This basically
involves moving your mailboxes to the standby server by changing
serveral Exchange related attributes. Because your primary server is
down, you cannot move the mailboxes using Exchange System Manager,
therefore you will have to manually update the attributes which a move
mailbox would perform.  You can also look into upgrading to 2007 which
has built in DR features ie. LCR; CCR; SCR.

Exchange: BCP Planning Exchange 2003
http://msexchangetips.blogspot.com/2007/05/exchange-bcp-planning.html

MS has an article "How to Re-Home Exchange Mailbox Account"
http://technet.microsoft.com/en-us/library/bb124766.aspx

James Chong (MVP)
MCITP | EMA; MCSE | M+, S+,
Security+, Project+, ITIL
msexchangetips.blogspot.com