[Samba] How to add a client to a domain?

[quiztli at lavabit.com]

Hello

I have recently "inherited" a small domain consisting of a linux server
running samba 3.6 and one client computer running Windows 7.

I want to add another client (also running Windows 7) to the domain.
Previously adding clients has been done by manually creating a linux
machine account and samba account.

I have created the accounts for the new client but when I try to configure
it to be part of the domain a window pops up prompting for an account and
password "that can join the domain". I don't really know what to enter
here and I am unable to add the machine.

Quoting from the documentation:
http://www.samba.org/samba/docs/man/Samba-HOWTO-Collection/domain-member.html#machine-trust-accounts

"When the user elects to make the client a domain member, Windows 200x
prompts for an account and password that has privileges to create machine
accounts in the domain."

"A Samba administrator account (i.e., a Samba account that has root
privileges on the Samba server) must be entered here; the operation will
fail if an ordinary user account is given. The necessary privilege can be
assured by creating a Samba SAM account for root or by granting the
SeMachineAccountPrivilege privilege to the user account."

What should I do sucessfully add the client to the domain?