ok ...first you must understant that everyone arround here .. those trying to help ... are pro`s..and i must admit that card on that kind of sistem it`s a joke indeed and many guys made a lot of jokes on it ... the card is simply to powerfull for that sistem...but there is hope ..listen...
i`m going to help you......first you must increase the amount of sistem ram ....try to find some additional RAM ..maybe 256 or higher ..than you test the sistem again and yuo`ll notice same improvement..
well 512 ram will do on many games..but for newer games .... you need 1024..this is the problem my friend that card is biuld to perform ...and newer games need a huge amount of RAM.... still there are going to be problems that hdd of yours is quite old and slow ..but first you must increase RAM.......
good luck