if some Service or other has been disabled.
If this worked before what has changed since then?
Access your Services Console through Administrative Tools in the Control Panel, and scroll down to see if "Power" is Automatic or Disabled. Double click the entry to display its Properties and if it is set to Disabled, change that to Automatic, then Start the service.
Another way is offered in the link below;
http://www.bytetips.com/enable-or-disable-windows-hibernation-in-windows-vista/
See if either works.
Mark
The Sleep/Hibernation option on my computer is gone. I used to use it all the time but now when I go to the list of power modes, I can't even click on Sleep. I see the option but instead of being in regular font like the other options it is just gray. How can I change this? I have Vista Basic. Thanks

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