I looked a bit around in my nvidia drivers, and i noticed under features and i saw that the Windows Media Pack was marked with a red X, but i already installed it.
I tried several things to make it work, but what seemed to work in the end, was changing my operating system language from danish to english, and downloading the Windows Media Pack again. So i wonder if there are different things in the Media pack country dependant?
If you have Nvidia Geforce experience, you can go to the settings under general, and then check the features if the Media Pack is missing or not.
Hopefully this can help someone.