In October 2013, Microsoft released Windows 2012R2, containing many improved features. A good article outlining those improvements can be found here: http://www.petri.co.il/whats-new-in-windows-server-2012-r2.htm#

Although installing the Hyper-V Role is straightforward on a new system, I have seen couple of scenarios where the Hyper-V role will fail on installation. Scenario conditions are outlined below:

Fresh install of Windows 2012R2 Server.

All Windows Updates applied then rebooted.

Post reboot, Hyper-V Role was installed.

Rebooted machine to finalize installation of role

Machine begins applying, gets to 99%, then fails to install the Hyper-V role. Windows performs rollback.

Resetting Windows Registry Files To Fix Hyper-V Role

The fix that worked for us was to open up a Command Prompt and select Run As Administrator (or create a batch file and run as an administrator) with the following text.