Question

When a database in the Treeview of SQL Server Management Studio is right-clicked and is taken offline and then the Delete option is chosen, is all space allocated to the database released back to the o/s file system pool?

Answer 1

If you take the database offline before deleting it, data files will not be deleted from disk. Please see this section of the books online.

http://msdn.microsoft.com/en-us/library/ms178613.aspx

Dropping a database deletes the database from an instance of SQL
Server and deletes the physical disk files used by the database. If
the database or any one of its files is offline when it is dropped,
the disk files are not deleted. These files can be deleted manually by
using Windows Explorer. To remove a database from the current server
without deleting the files from the file system, use sp_detach_db.