In an NT/W2K domain model, a computer actually exists as an object in the security accounts database, and the computer itself actually authenticates to the domain controller, even when nobody is logged on.
With Win9x clients, the *user* of the client computer authenticates to the domain for access to resources.
To answer what you probably intended to ask, yes, users on 98/95 machines can log on to an NT/W2K domain.