see
Exchange 2003 Backup and Restore with NTBACKUP
http://www.msexchange.org/tutorials/Exchange-2003-Backup-Restore-NTBACKUP.html
http://www.outlookexchange.com/articles/HenrikWalther/RSG.asp
http://www.petri.co.il/restoring_exchange_mailbox_recovery_storage_group_part1.htm
How to Restore Exchange to Recovery Storage Group
http://support.microsoft.com/kb/824126