Null Session

Hi all,
In my network lab I have a Windows server 2003 sp1 (in a workgroup) wich I
use to store some documents. For ease of use I would like to share a folder
in an anonymous logon; so I set the anonymous logon user in the share and
NTFS permissions, but all my attempts to log on anonymously have failed so
far.
Are there any further settings to be triggered to allow the above null
session?
Thanks in advance for your help and have a nice week-end.

--
Leonardo