How to Delete hiberfil.sys When Hibernation is Not Supported by Firmware

When "powercfg -h off" doesn't work, then disable it using the registry (usual warnings about possibly messing up your registry):

Run regedit, and browse to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Power.
Change the value for "HibernateEnabled" to 0 (zero).
Click OK and restart.

(See article by Fergus Macdonald.)