J500s:
you might want to try FSautostart,it a program that allows you to shut down alot of needless background program.you can set it up to run almost any game and it will automaticaly reset your computer to it's {normal} configuration after you end
the game{program}. it's relatively ez to setup,if I can do it anyone can.

Also I noticed that you have 512 mb of ram memory,doubling that to a gig of ram,may help and stablize your FPS and it's kind of cheap to do these days.
Another thing,your resolution,I assume that the native for your monitor.Try going into the video settings of the game,first page at start,and check your texture size,it's likely 512 mb I think thats default.You can adjust this down to 256mb but before you do that look at the resolution the game is set at,if it's the same as your monitor you might want to downsize that first.
You'll have to experiment,only change 1 thing at a time,and then check to see if you get improvements.1 other thing,the game allows you to set a max frame rate,30,60 and unlimited.If you have a LCD monitor set it to 60 as thats the refreshrate of most LCD's. you can use 30 too on a low end machine,give it a try,Ideally you want the frame rate to be steady so 30 fps steady is better than 60 to 20 to 45 to,well you get the idea.This helps by stopping your video card from making needless rendering and allows it abit of head room.
It would help if we knew your type and speed of CPU,vidcard,memory,etc. When you get back from fishing remind me and I'll see if I can walk you through some of this.
There's plenty of guys in the squad that know more about this than I do,I know just enough to be dangerous.... fair warning...
Morf