Without knowing more, I agree with the above comments that 4 Gb of RAM is hindering your performance.
Depending on the game(s), your CPU may also bottleneck if you're running at stock.
Assuming all your parts are working properly, I'd recommend purchasing another 4Gb of RAM (exact same RAM you have now, if possible. If not, get the same speed/timing - you will not benefit from buying faster, more expensive RAM if you keep what you have in your system). I'd also recommend overclocking with an aftermarket cooler.
Until we know more, that's about all we can offer.