How to Fix Hibernation in Windows Vista
If the hibernation option is missing from your Vista power options, it’s possible the Hibernation file cleaner was removed from the computer. It seems this can be done using Window’s built in Disk Cleanup utility. Below are the steps to create a new Hibernation file cleaner and restore the hibernation option to the computer:
- Open the Start menu
- Type cmd in the search field (this is the same as going to Start>Run, but I don’t believe “run” appears by default in Vista with the new start menu)
- Type powercfg -h on
- Press ENTER
If you did it correctly, there should be no output on the screen other than another prompt waiting for input. Check your power menu now to see if hibernation appears. Mine immediately appeared as the default option when clicking the power button on the start menu.
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