Sharing "user level" access

Hi,

I've got a Win2k3 SE Server setup with a mixture of XP and 98 Clients (both
standard and SE).

I've managed to change the share method from share level to user level
access and it successfully reads the user list from the domain server.

I've created a c$ share and i've added domain admins as the full access
user.

The problem is that up to now the sharing system only seems to be working on
one out of the 3 machines (win98 se).

The other 2, (standard and SE dont work) and when u try to connect you get a
continuous prompt to enter a password for "localmachine\guest"

On the machine that does work, there is no "remote administration" account
enabled.

Does anyone know why the other 2 machines dont work?

Thanks

Neil D.