Today I run out of space on my C: drive, so I used the Desk Clean up wizard to free some desk space for me, it asked me to clean many things and I blindly checked them all.
Then when I tried to Hibernate the computer, I didn't find the Hibernate option.
Thanks Google, I found a Microsoft KB Article (The Hibernate option is not available in Windows Vista http://support.microsoft.com/kb/929658)
The article says "This issue occurs if one of the following conditions is true: 1) The Disk Cleanup Utility and has been used to delete the Hibernation File Cleaner. " and there are some other conditions ... but what I did to clean my disk space prevented me from Hibernation !!!!
Hmmm, Is it my fault any way ... I shouldn't check all the items in the wizard :(
Oh, I forgot to tell you how to get Hibernate again ... on the command prompt type:
|powercfg -H ON|