Using two CPUs to its full potential?

Now I don't know much about CPUs, processors, that kind of stuff, but whenever I play a game one processor always lacks in compared to the other. Here is an image with me having "Day of Defeat: Source" minimized while taking a shot of the task manager:

So is there anything I can do about this, or is it normal to have this? I would like my FPS count to go up in some of the games that I play. Here are my computer specs, just change the RAM amount to 1.5 GB instead of 1 GB and the graphics card to a Radeon HD 4670:

http://www.superwarehouse.com/Sony [...] /ps/617486

Thanks in advance for any replies that may help me.

your board supports nothing but the older pentiums, core 2 will not work with the 915 chipset.