Advice on Graphics Cards

[Abriael]

you need a new PC buy a cheap one with a newer 4 core CPU and atleast 6GB of ram and buy a decent videocard like amd 6000+ series or nvidia gtx580 or higher.
you could build one but you need to know puters.

your CPU is close to 10 years old.

6GB of RAM are good only with a triple channel architecture (that depends on the chip). 4 GB are actually plenty for most gaming needs, and if your chip supports double channel, better than 6.