I need help!

[Valiant1]

My current system is running a phenom II x6 1055t, a 7870 and 8GB of ram. I have scoured the internet trying to find out what is wrong and so far no luck. In a nutshell, everything I try and run is running around 25-30 frames. And I downloaded this to give windwaker another try since it has been a few years and game grumps got me thinking about it. And it runs too slowly for me to play and after a few minutes it will drop to 11fps and the screen goes black. Just the game screen though. My items and health and everything still show up and the save screen works fine. But it is all running at 11fps and if I die it works for a few sec then goes black again. Any ideas?