In reality chances are you PC will not support a quad CPU, you will probably have to upgrade your mother board first, and then it depends A LOT on your graphics card and ram as well, you best option to play bad company on a medium setting will be to upgrade you pentium 4 cpu to a nice affordable core2duo something like a E7600(low budget) or a core2duo E8200 8300 even the E6xxx series will duo way better (much much better) than the pentium 4 you have installed now and you can buy them now for around $50-80 bucks. but make sure your mother board can handle such CPUs before you buy.