could be a problem with the drivers, download the latest nvidia drivers: 77.72 from thier website.
Id also think about updating the motherboard chipset drivers and if its built in sound those drivers too.
and once the game loads put all the options on the lowest setting to make sure it`ll run then slowly put them up to medium etc until you get to a level which wont affect performance.
With those specs you should easily run the game on medium settings.