The Windows Server 2012 July 2013 update rollup is an important one to install on Hyper-V servers.  Specifically because of this update:

2853952  Active Directory database becomes corrupted when a Windows Server 2012-based Hyper-V host server crashes

While I have been running Active Directory with no problems on Windows Server 2012, I have talked to customers who were effected by this, and AD recovery is never a fun operation to perform.

You can download this update from here:, or you can just receive it through Windows Update.  Note – there was an issue when this update was released last week that caused crashes on some systems.  This issue has been corrected and an updated package has been posted.