After all my downloading exploits I had ended up with around 50 MB left on my hard drive.
I attempted to play Oblivion, but was running on all low settings, reduced draw distance and no grass and it was still slightly choppy. This is on a high end PC.
Now I have 13.8GB free after a mad deleting spree and it runs max perfectly.

So there you go, a lesson for you all to clean your disk drives if you're having trouble.