I was rather puzzled today that when I closed the laptop lid, it did not go to hibernate as usual but instead to sleep. I thought it had to do with the power options that for some reasons, they have changed. Interestingly, the hibernate option disappeared. Only sleep and shutdown were available.
After tumbling around, I checked out with google and found a helpful site http://www.reviewingit.com/index.php/content/view/32/2/ . It suggests to run “powercfg /hibernate on” in the dos prompt as administrator. It worked instantly and the hiberate option reappeared.