Ok,

1. go to your video card control panel and make sure everything is on application controlled
2. make sure your drivers are up to date
3. find out what you maximum res for your monitor is
4. go into the game and use these settings and got to options
5. put overall on about high,
6. then weather go 80% on everthing,
7. Arcraft crank that baby up,
8. Hardware,
   a. res to 1024x768x32 (now depending on you frams and what your monitor can do you can keep going up in res and checking it)
   b. turn off the box marked Antialiasing,
   c . turn it from trilinear to bilinear,
   d. dynamic lights 4 or 5 and for the one below it 4 or 5,
   e. global terrain just go high, set your frames at about 40 and lock them.

now report back to me on how its running ie your frame rates then we can start bumping it up from there

You have a great computer, its just if you dont have this came configured right it will suck up alot of CPU and Ram, also make sure not alot of background programs are running and do a defrag of your HDD as well

Shelldrake, could you enlighten me on what tweaks you made to windows, etc. Thanks.