definetly need to upgrade to keep up with the newer games.. New processor, RAM and videoboard.. If you are happy with the harddrive space you have now maybe a barebone system would be better for you.. Good luck.
darkworksgraphics care fine and ive ran games fine on my pc, its just the lag
Because you're computer is struggling.
I am suprised CoD2 runs.
Buy a new PC....That's all I can advise you to do.