Need some help with NetGroupAddUser

[kcollins15 at cfl.rr.com]

New B question -- Need help with win32net.NetGroupAddUser.  I used Mark Hammond 
sample code to create a new user from his book Python Programming on Win32. I 
then added one line to add the newuser to a group.
def CreateUserAndShare(userName, fullName):
    homeDir = "%s\\%s" % (serverName, userName)
    # Create user data in information level 3 (PyUSER_INFO_3) format.
    userData = {}
    userData['name'] = userName
    userData['full_name'] = fullName
    userData['password'] = userName
    userData['flags'] = win32netcon.UF_NORMAL_ACCOUNT | win32netcon.UF_SCRIPT
    userData['priv'] = win32netcon.USER_PRIV_USER
    userData['home_dir'] = homeDir
    userData['home_dir_drive'] = "P:"
    userData['primary_group_id'] = ntsecuritycon.DOMAIN_GROUP_RID_USERS
    userData['password_expired'] = 1 # User must change password next logon.
    
    # Create the user
    win32net.NetUserAdd(serverName, 3, userData)
    win32net.NetGroupAddUser(serverName, "Administrator", userName)

This is my error:
pywintypes.api_error: (2220, 'NetGroupAddUser', 'The group name could not be 
found.')
What should I be using for the groupname parameter, I've tried them all, 
Administrator, Guests, Users ext.... Any help will be greatly appreciated. 
Thanks,
kc