You are connected as printer admin or root (this is not the “Printer Operators” group in NT, but the printer admin group as defined in the [global] section of smb.conf).

Copy all required driver files to \\SAMBA\print$\w32x86 and \\SAMBA\print$\win40 as appropriate. They will end up in the “0” respective “2” subdirectories later. For now, do not put them there; they'll be automatically used by the adddriver subcommand. (If you use smbclient to put the driver files into the share, note that you need to escape the “$”: smbclient //sambaserver/print\$ -U root. )

The user you're connecting as must be able to write to the [print$] share and create subdirectories.

The printer you are going to set up for the Windows clients needs to be installed in CUPS already.

The CUPS printer must be known to Samba; otherwise the setdriver subcommand fails with an NT_STATUS_UNSUCCESSFUL error. To check if the printer is known by Samba, you may use the enumprinters subcommand to rpcclient . A long-standing bug prevented a proper update of the printer list until every smbd process had received a SIGHUP or was restarted. Remember this in case you've created the CUPS printer just recently and encounter problems: try restarting Samba.