While working on project of database backup and recovery, I found out that my client was not aware of the resource database at all. The Resource database is a read-only database that contains all the system objects that are included with SQL Server.
Location of this database is at different places in the different version of SQL Server.
In SQL Server 2008:
<drive>:\Program Files\Microsoft SQL Server\MSSQL10.<instance_name>\Binn\.
The Resource database cannot be moved.
In SQL Server 2005:
Same place where master database is located.
The Resource database have to move with master database.
You can run following commands to know resourcedb version and last updated time.
SELECT SERVERPROPERTY('ResourceVersion') ResourceVersion, SERVERPROPERTY('ResourceLastUpdateDateTime') ResourceLastUpdateDateTime GO
Reference: Pinal Dave (https://blog.sqlauthority.com)