One pet-peeve I’ve found with Vista (generally, despite the public hate, I like it) is that hibernation feature tends to disappear… usually due to a disk cleanup.  Essentially, when the hibernation save file is deleted, Vista removes the hibernation ability.

Luckily, turning it back on is very easy.

Click the “Start” button, and type cmd… then press Ctrl+Shift+Enter to open in administrator mode. You can also right-click the item “Command Prompt” in the menu and choose Run as Administrator.

From the command prompt, type in the following command:

powercfg /hibernate on

You may have to restart your computer before it will take effect, however I’ve found that it enables hibernation immediately in most cases.

If this doesn’t work for you, there are some alternative methods, but this should work in 98% of the cases.  If it doesn’t, feel free to comment here, and we can shoot you some other ideas.

Enjoy your hibernation!