Here is detail instructions: http://msdn.microsoft.com/en-us/library/ms345408.aspx .

Why you restarted server, I usually use that script for model:

SELECT name, physical_name AS CurrentLocation, state_desc

FROM sys.master_files

WHERE database_id = DB_ID(N'model');

ALTER DATABASE model SET OFFLINE;

--Move files

ALTER DATABASE model MODIFY FILE ( NAME = modeldev, FILENAME = 'new path');

ALTER DATABASE model MODIFY FILE ( NAME = modellog, FILENAME = 'new path');

ALTER DATABASE model SET ONLINE;

SELECT name, physical_name AS CurrentLocation, state_desc

FROM sys.master_files

WHERE database_id = DB_ID(N'model');