If I understand hibernation correctly it is a form very deep sleep. But, what I have never figured out is the following. I had several computers over the past 8 years or so and even with the Macs, I have never had a computer that was really capable of using deep sleep or in this case hibernation. Every time I have tried it the present machine I have (HP a6300f) never ever wakes up. So I guess my question is do very many people use this feature and if so how do they get it to work?