Well real quick, 4 cores/4 threads is i5. i7 would be 4 cores/8 threads. Each of your cores equals one thread. So it's not that you have 4 cores and 4 threads, it's that you have 4 cores that are 4 threads. That's why you get an i7 over an i5, the 4 hyperthreaded cores.
and it could, but if you set things higher in the graphics, your GPU will take over a bit more. Try turning anti aliasing off, and textures to medium.
edit: [strike]Also, what resolution is it? You didn't answer that in your last post[/strike]
Just saw the last post, that should be fine