On Windows 8.1 and Server 2012 R2, SMB 1.0 (aka CIFS) is no longer enabled by default. This means clients that don't support at least SMB 2.0 (for Windows: everything predating Vista/2008) can no longer directly connect to a 8.1/2012R2 server, and instead, are presented with an error if they attempt to do so:

Error
The specified network name is no longer available.

You can re-enable SMB 1.0 support by installing the SMB 1.0/CIFS support feature on your server.

Some users reported that even after enabling this feature, they could not access shares on the server. Apparently, the SMB 1.0 driver is not loaded properly, because of a missing dependency on the Server service (aka LanmanServer).
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