I bought a factory made computer p6150t Series from HP, because i didnt have the option to build it

. But anyway this is what its composed of:
Genuine Windows Vista Home Premium with Service Pack 1 (64-bit)
Intel(R) Core(TM) 2 Quad processor Q8300 [2.5GHz, 4MB L2, 1333MHz FSB]
Memory 4GB DDR3-1066MHz SDRAM [4 DIMMs]
Hard drive 640GB 7200 rpm SATA 3Gb/s hard drive from 500GB
Graphics card Integrated graphics - Intel(R) Graphics Media Accelerator X4500 [VGA]
Im thinking of upgrading the graphics card, and adding more RAM, any ideas? And how it is right now, what games could it handle? Thanks