I have the same problem.
My Win 7 laptop is set up for "workgroup," which is the network name of other computers on my LAN.
When I try to connect, Win 7 sees the other computers, but selecting one, I get that popup that says at the top "Network Password." Then lower, fill ins for the user name on the computer I'm trying to connect to and the next line: password for the user I'm trying to connect to.
Below that it tells me I am a member of a domain, that has my laptop's name.
But the Laptop is set up to be a member of the "workgroup," not a domain.
So, no log in to the other systems is working. A domain computer won't be able to connect to a work group. Even if Win 7 telling me I belong to a domain is incorrect, any user name and password I enter for the computer I'm trying to connect with does not work. Another popup comes on asking me to enter the network password.
i also tried entering the password of the LAN, thinking that might solve it but it didn't.
and I tried entering the name of the user, with just the user name, as well a username using it's complete location on the network: \\(computer
Nothing works and I can't connect to other compturers on the LAN.
And as this thread say's, Win 7 is saying I'm a member of a domain.
So, same problem here.
Oh, I also set up user accounts on the Win 7 computer with the same name and password as on the other computers in the LAN--but that didn't do any good, either.