samba - Sep 2000 - Changing permissions of files and direcrories on SAMBA mounted drive

Hi,
    I am a new user to SAMBA. I have installed SAMBA
    on a linux server. And I have mapped the share
    on to my Windows 2000 machine. Both the SAMBA 
    server and Windows 200 machines are in the
    same domain. I have set security=user.

    And I tried creating some files and directories 
    on the share that I have mapped on my Win 2000.
    By default it creates the files and direcroties
    with 777 permissions(It is defined in the config file). 
    But if I try to change the permissions of the file 
    or directory, then I cant change the permissions.
    Is it a configuration problem or something else to be
    done to get proper access to the files ?

    Please give me suggestions. I am badly in need of
    this one working.
    I login as a domain user into my system.
regards,
Goud
==============================================Basavana Goud B
Software Engineer, WIPRO Global R & D,
#8, 7th Main, 1st Block, Koramangala,
Bangalore - 560034. Ph: 5530035 Extn: 1019.
email: basavana.goud@wipro.com
www.wipro.com/uwin