If you are like me, and wonder where all the space on C: went, you might have also stumbled across hiberfil.sys file, which is usually taking a couple of gigs. This is especially important if you are running your system on precious SSD space.

Luckily, you can get rid of that file, and the fastest way is to use command prompt. These guys say it should be elevated, but it worked just fine for me, probably due to disabled UAC. Anyway, here is a command that works:

powercfg -h on

No need for a restart! The file should disappear right away.

I personally prefer this approach over struggle with Power Options UI of Windows 7.