colwyn,
Assuming you have a full backup of 2003, treat it as a XP box. Run the registry insert located on your SME server and modify the domain security settings as described by several postings to add 2k/XP to SME domain.
If stock SME, (samba < 3), beaware that ALL SME users are added to the administrators group on the Windows box. I suggest removing the linux users group and adding root, admin, and any other accounts you want to have full admin privs....
ryan