One critical detail is missing: Right-click Command Prompt and select "Run as administrator." Then the command will work.
So, the complete instructions are as follows:
Click Start -> All Programs -> Accessories
Right-click Command Prompt
Select Run as administrator
Grant permisssion to change system settings
In this privileged command prompt window, enter: powercfg -h off
Poof! hiberfil.sys is gone -- instantly!