Dell Optiplex 790: 3.1 GHz I5 Quad-Core, 8GB DDR3 RAM, 750GB HDD, Pegatron G310 512MB Graphics w/HDMI, 64-bit Windows 7 Professional. Dell Optiplex 790: 3.1 GHz I5 Quad-Core, 8GB DDR3 RAM, 500GB HDD, Pegatron G310 512MB Graphics w/HDMI, 64-bit Windows 7 Professional