storm slider said:
At 1600x900 with 30 FPS or above?
There's no such thing as "max settings" for GTA IV as it's very poorly optimized and it'll kill your card quickly; you will have to mix details a bit and see what results you'll get. Most likely you will get more than 30 FPS at that resolution, but I don't think you'll be able to enable max settings and still get more than 30 FPS.
It will also depend on your amount of RAM and CPU, especially a quad core CPU; if you've got one, GTA IV will run a bit better. Not much better, but still.