Hi Kenji,
Version 6.51 was very old and may have some issue.
Latest version 7.8 is officially supported on Windows Server 2012. Please install the latest version and let us know if you face any issues.
It seems that 6.51 was installed on your machine some time back.
We no longer push the drivers via windows update. Hence you can update the same by using the installer.
Regards,
Ashish
Ashish