How to disable and re-enable hibernation on a computer that is running Windows Vista

To make hibernation available, follow these steps:

• Click Start, and then type cmd in the Start Search box.
• In the search results list, right-click Command Prompt, and then click Run as Administrator.
• When you are prompted by User Account Control, click Continue.
• At the command prompt, type powercfg.exe /hibernate on, and then press ENTER.
• Type exit, and then press ENTER to close the Command Prompt window.
  
• Easy step - [windows button + R] and in the prompt enter the above command.

To disable hibernate options follow the above steps except the command should be "powercfg.exe /hibernate off"