Filestream is a new feature that came along with SQL Server 2008. You need to enable FileStream before using it.
If you google, syntax for enabling FileStream is EXEC sp_filestream_configure @enable_level = 3;
However, you will end-up with Could not find stored procedure 'sp_filestream_configure' error.
Above syntax if for CTPs not for RTM!. So the correct syntax follows.
EXEC sys.sp_configure N'filestream access level', N'2'
RECONFIGURE WITH OVERRIDE