If you don’t see Hibernation on the Shutdown options, then its probably disabled, or Hybrid Sleep is enabled.
In Windows XP, you could enable and disable Hibernation via the GUI. However starting with Windows Vista, you have to use the following command in Command Prompt:
powercfg /hibernate {on|off}
Starting with Windows Vista, there’s also a new power option, called Hybrid Sleep. It’s a combination between Sleep (saving to memory and going to low power mode) and Hibernation (saving to hard disk and turning off). It saves to both memory and the hard disk and goes into the low power mode, letting you resume quicker while safeguarding your opened documents from a power outage.
You can enable/disable Hybrid Sleep via the Power Options dialog: click Change when the computer sleeps > Change advanced power settings > Advanced Sleep options > Sleep.
