|Looking at what you have for specs - intel core 2 firstname.lastname@example.org ghz (E4500?)- why would you even consider a "core 2 duo E6600 @ 2.40 Ghz"? If you have a decent motherboard & are willing to overclock, your current CPU should easily overclock to 3.0GHz or higher. I see no reason to upgrade the CPU, even if it is to a quad, unless you can get it really cheap.|
Also, 3GB RAM isn't very much RAM these days, especially for gaming. And if you want decent gaming performance, you'll need a decent gaming graphics card, not integrated graphics or a low end card.
Please clarify your system specs.