in Vista it indicates if certain files are removed that feature will not work.
Go to the cleanup utility and see if you have removed these files. Highlight each of the items listed to be cleaned and read the message... tells not to remove if you use the hibernation feature.
Do not how to retrieve these if they are deleted... maybe a repair or reinstall of the operating system. If you operating system has the feature, from the "run" command you could try "sfc /scannow" without the quotes and a space before the slash (/). Might be worth a try.
a couple month ago i did a disk cleanup (i now use ccleaner) and ever since hibernation wont work any help?? (i might upgrade to win 7 beta)