One of the most common problem in Windows Vista is the missing "Hibernate" option in start menu. I get many mails regularly asking the same question: How to enable the hibernate option in Windows Vista?
Actually its a known issue in Vista. The hibernate option automatically disappears whenever you run "Disk Cleanup" wizard. It happens because Disk Cleanup wizard also removes important Hibernate files to free up space on your hard drive. So if you use Hibernate feature, then make sure you always deselect "Hibernattion File Cleaner" option from the list whenever you run Disk Cleanup wizard in future.
Anyway its very easy to re-enable the missing Hibernate option. If you are also not getting the option, you can bring it back by following these simple steps:
1. Click on "Start button -> All Programs -> Accessories". Right-click on "Command Prompt" and select "Run As Administrator". If you are prompted to enter password, enter the password and continue. You can also open Command Prompt in Administrator mode by typing "cmd" in Start Menu Search box and press "Ctrl+Shift+Enter".
2. Now provide any of following commands:
powercfg /hibernate on
powercfg -h on
3. Exit command prompt and Hibernate option should appear in Start Menu.
So next time when you run Disk Cleanup, make sure to uncheck the option to clear hibernate files otherwise it'll again disable the hibernate feature in Windows and you'll not get the option in Start Menu.