OP, your cpu will overclock past 4ghz and be more useful when using this http://www.newegg.com/Product/Product.aspx?Item=N82E16835103099 You will see more improvement by doing this.
Your video card is a bit dated but it should be fine as long as you turned off shadows, bloom, and aliasing, experiment with the other graphic settings.
Also, download and install this important direct x update that most people miss. It made a difference for me. http://www.microsoft.com/en-us/download/details.aspx?id=8109
Your 8 gigs of ddr2 is fine.