adding users to db

I have an application where users are members of different NTFS groups. If I
add a new client I add a new group. I would like to be able to do this from
asp.

I know how to create a new NTFS group but how do I then add that user to MS
SQL 2000, then give that user permissions on the clients db and some stored
procedures. I am on Win 2003 running SQL 2000.

Thanks for any links.

Mike