Hibernation goes one step beyond sleep mode when dealing with an inactive workstation. Whereas sleep mode minimizes the amount of power a system draws by disabling certain hardware and stepping down processing power, hibernation completely prevents a system from drawing power by saving the state of the current system RAM and saving it to disk. This works very effectively, but if you try to configuring it in Windows Vista or Windows 7 you may be shocked to see that you can’t do so from the GUI. If you browse to advanced power settings you will find options for configuring a time until sleep mode takes effect, but that’s it.
Although there is no GUI to enable this, you can enable hibernation from the command line with the powercfg utility. The following command will make hibernation configurable in the GUI: powercfg –h on. Once you issue this command you will be able to configure the time until system hibernation in the advanced power settings control panel window.