I'm pretty sure these operations need to done as the Administrator. one way which is pretty easy is to make a shotcut to /windows/system32/cmd.exe. say on the Desktop. IThen run the program (CLI) as Adminsitrator. If you don't need the shortcut f0r future use just run /windows/syte32/cmd.exe itself as Admnistrator. . When you have a command window open as Adminstrator. - Window will ask for confirmation - the run "powercfg -/h on. I believe dthat isi the right syntax. Google powercfg to make sure. Leep in mind tht the hidden file in the root directory (hiberfil.sys) may grow very larger ove time - it could even eat up most of your free space.
Sorry for beinig so long-winded. I want to actually do the reverse and kill the hyperfil.sys since I don't use hibernation on a desktop computer.