Hibernating Vista
If you've established that the Hibernate choice is absent from Windows Vista, it’s possible it is because of the hard disk cleanup option that deleted all the files used in the hibernation process. But its not a major problem, getting your Vista to hibernate again is the easiest thing to do.
Enter cmd onto the begin menu seek box, then utilize Ctrl+Shift+Enter to run as an admin. Running as an admin can be also done by choosing the option after a right click.

On the dos window, type in as it is shown below:

That is all you are requested to do. Except the usual restart of windows!
Sometimes Hibernating Vista may become a tough thing to do, otherwise its a simple process. The problem may be junk files in the Windows Registry. You need to scan your PC with PC DOC PRO registry cleaner which will fix this error.