OK we are not talking about a lot of ram we are talking about four gigs. Even though we are talking about duol core that doesn't mean much considering they still make duol cores, and some duol cores are faster than some quad cores. My advice is to upgrade the processor on the moth board. In order to upgrade the motherboard you will have to look up how it works.
Besides the current advice, I have a few resource recommendations. Everyone always says the most important upgrade is the hard drive that will affect the paging file speed. Appearently people feel the hard drive affects speed especially with virtual memory, and the paging file in this area i know two things that can speed you up. Are you using a I.d.e. hard drive, if you are then a Sata drive will make a difference inspeed. You can raid multiple hard drives to speed up your system.
Another question if you add more virtual memory would that make a difference. Hear me out, this is my reasoning it would require fewer times you would have to load your paging file. Would this make a difference I don't know.
An easier idea is to go to your graphics option in the game and lower everything. This will speed up the game, but everything will look worse. I think the gameand windows should have the same graphics resolution.
Now windows can be tweaked for performance. Forgot how to find system options. This will make windows look worse. This should at least load fewer things in memory freeing up room for thegame. You can't see windows while you play the gasme anyways.
Windows by default loads with balanced power options. Some reason manufacturers either leave this alone, or create their own plan. Even on high performance this can be turned up. Go into the power options, and tweak the power plan. If you have a desktop who cares if you use a little more power.
Let's not forget about over clocking if your motherboard allows it,and if have the cooling if your system needs it.
Finally you can go into your graphics options. Make sure your computer is using the card. The manufacturers don't turn this on. This option is in you graphics control panel, or whatever the graphics company calls the software that controls the card. You can set the card to over ride the game graphics settings. This will alleviate processing to the card. I don't know this should also work in speeding up your system without upgrading.
If someone could clean up my responce, and responds with their input it is probably needed.
I am wondering if you enabled plug and play on the motherboard, can you disable plug and play in windows. If you could do this wouldn't it speed up by not requiring hard drive, or ram space. PS. I'm not accepting blame for all this crazy advice on how to speed up your computer without paying much extra money.