If you can't join Windows 7 to Samba domain, then check Windows 7 machine registry for the next records:

For newest Samba (3.5.x for ex.):

        HKLMSystemCCSServicesLanmanWorkstationParameters
            DWORD  DomainCompatibilityMode = 1
            DWORD  DNSNameResolutionRequired = 0

       HKLMSystemCCSServicesNetlogonParameters
           DWORD  RequireSignOrSeal = 1
           DWORD  RequireStrongKey = 1


For Samba 3.3.x 3.4.x

        HKLMSystemCCSServicesLanmanWorkstationParameters
            DWORD  DomainCompatibilityMode = 1
            DWORD  DNSNameResolutionRequired = 0

       HKLMSystemCCSServicesNetlogonParameters
           DWORD  RequireSignOrSeal = 0
           DWORD  RequireStrongKey = 0
phone +372 5507447 mail me