Hibernation is a Windows' feature that's intermediate between totally shutting system down and putting it to sleep. It lets you boot more quickly than that complete shut down and uses less power than sleep mode. It comes in handy when you have to return back to working on your system in order attend to a pressing matter. To check if hibernate is enabled on your system;

step 1. Open Control Panel
step 2. Click Power Options
step 3. Click Choose what the power button does
step 4. Click Change settings that are currently unavailable

If you see Hibernate under Shutdown settings, the feature is enabled, else go to step 5 & 6

5. Select the Hibernate checkbox
6. Click Save changes

Or just open the command prompt by typing cmd on windows search box and type:
powercfg -h on

It works on Windows 7 as well