I am with Hyppy. You are probably going to have to do is using sql permissions unless you either add them to your domain, or they are in another domain with a trust relationship. Another, but poor way, would be to make sure that the administrators both have the same password, and then add a local administrator with the same password: Pass-through authentication may work there.
I would add a SQL user, give it the appropriate permissions, and use that to connect from the foreign computers.
P.S. Your 0% accept rate is very conspicuous. You should go back and accept any answers that have helped you.