Yes you can run GTA IV on medium settings I had intel core 2 duo @2.93GHZ with 4gb RAM Nvidia 210 512mb on PC it lagged but your PC specs are higher then mines i think you'll get more fps.
Can you tell us the clock rate of your CPU, and the type of graphics card you're running? It's kinda difficult to tell you if you can run it with the data you've given us so far.
Yes you can run GTA IV on medium settings I had intel core 2 duo @2.93GHZ with 4gb RAM Nvidia 210 512mb on PC it lagged but your PC specs are higher then mines i think you'll get more fps.
Having first hand experience running it with a first gen i5 and a discrete GPU (Not as much VRAM as yours but still) I honestly wouldn't bother the kind of graphical fidelity you would be running with to get a half decent frame rate would be probably looking worse than the last gen console version. It will run but look a total eyesore.