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: 
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.
For forcing remove of hibernation file and mounting it use this:

```
sudo mkdir /media/Windows
sudo ntfs-3g -o remove_hiberfile <device> /media/Windows
sudo umount <device>
sudo mount <device> <mountpoint>

```

Instead of `<device>` use the correct device like /dev/sda4

**Update**

Sorry, I don't know why, but I thought you want to mount it on linux.

So, for removing it you can use a Live-CD, like ubuntu, and execute these command above.