Your PC should easily manage this game looking at the specs here click here so unsure what to suggest,could try this you,
click here this will turn off most of your unneeded back round processes. I have tried it myself but really have not got a clue as to whether it works as I have quite a high spec self build anyway, and there isn't a game out there that I cannot run on high settings. But I think it might be worth a try. Remember to switch everything back on after gaming.