look here: How to: Restore a Database to a New Location and Name (Transact-SQL), which has a good example:
This example creates a new database
named MyAdvWorks. MyAdvWorks is a
copy of the existing AdventureWorks
database that includes two files:
AdventureWorks_Data and
AdventureWorks_Log. This database uses
the simple recovery model. The
AdventureWorks database already
exists on the server instance, so the
files in the backup must be restored
to a new location. The RESTORE
FILELISTONLY statement is used to
determine the number and names of the
files in the database being restored.
The database backup is the first
backup set on the backup device.
USE master
GO
-- First determine the number and names of the files in the backup.
-- AdventureWorks_Backup is the name of the backup device.
RESTORE FILELISTONLY
FROM AdventureWorks_Backup
-- Restore the files for MyAdvWorks.
RESTORE DATABASE MyAdvWorks
FROM AdventureWorks_Backup
WITH RECOVERY,
MOVE 'AdventureWorks_Data' TO 'D:\MyData\MyAdvWorks_Data.mdf',
MOVE 'AdventureWorks_Log' TO 'F:\MyLog\MyAdvWorks_Log.ldf'
GO
This may help also: Copying Databases with Backup and Restore