Recovery
From Mike's Wiki
Recovery from an Exchange database failure can be a nightmare. That said, the Recovery Storage Group in Exchange 2003 is a boon.
Open System Manager, right click on your Exchange server and select New Recovery Storage Group. Start a tape restore (You do have a backup don't you?) and it will restore to the Recovery Storage Group by default. Mount the Recovery Storage Group, right click on the mailbox you want to recover and select recover mailbox.

