I freshly installed Windows 8.1 RTM on my old laptop and the setup beautifully recognized all my devices and installed the drivers for them. However the Hibernate option didn’t show up in the shutdown menu. As a first try I enabled hibernation with the powercfg /h on command with no success.
It seems that after enabling hibernation, the Hibernate button must be enabled as well. On the left pane of the Power Options dialog you can find the Choose what the power buttons do action:
When the Define power buttons and turn on password protection dialog is displayed you can turn on the Hibernate button with administrative privileges:
Now you can click Hibernate in the old world:
And in the new world as well: