Question: Ok, so I know what hiberfil.sys is, and I want to use hibernation on my laptop.

But I have another hard drive active in my laptop, it's taken from my old one... and I want to get rid of the hiberfil.sys on that drive. But even with admin privileges I can't delete it.

Any ideas?

Answer: 
I wanted to do this in the easiest way possible, especially without rebooting.

Open a command prompt as administrator and go to the disk where hiberfil.sys resides. In my case:

```
C:\Windows\System32\> e:

```

In e:, check for hidden files:

```
E:\> dir /A:H

```

In the listing hiberfil.sys should show up. If so, delete it:

```
E:\> del /AS hiberfil.sys

```

I have to warn you: I don't know what happens if you do this with an active hiberfil.sys file. In my case it was on an old hard disk drive and was no longer needed.
If you really, really want to get rid of the file, you can always boot to something like a Linux or Windows PE boot disk, and then delete it.

If it was placed there by the current OS, it will come right back. However, from your wording, it sounds like it was placed on the old HD by an old OS that was on it.