As a part of disaster recovery, there may be a need of Restoring system database, i mean master,model,msdb database, below are the 2 simple steps to Restore system Database
Start SQL Server in Single User mode,It is very simple click on start go to run and type SQLServerManager10.msc( for SQL Server 2008) or SQLServerManager.msc(for SQL Server 2005),click on SQL Server Services. Select the instance .right click on the instance then properties-select Advanced tab.Go to Start Up Parameters and type -m,check the image below
Now SQL Server is running in Single user mode, no more connections are accepted,only
Execute the restore script using SQLCMD,Check the below image
when is done Start SQL Server normally by removing -m from the startup parameters.