As long as SQL server service is not starting you cannot restore the backup. So you will need to rebuild the system database. See BOL for the exact syntax.
Be aware that in SQL 2005 all system databases are rebuild, not just the master. So any jobs, maintenance plans SSIS packages etc. in the msdb need to be restored from a backup.
Hope this helps
Markus
[font="Verdana"]Markus Bohse[/font]