You can run them the same way you could run them on a system with 512 MB of ram @ 333 with a 64 bit integrated graphics card. A more useful question would be what settings could you run them on, to answer that question i need more detail like the speed of your ram and maybe the name of your processor or at least the company.
I beg to differ. I am running an Intel E6300 and nVidea 9600GT with 4GB DDR2 RAM. I CAN run GTA 4 on medium settings.
Yeah, but the 8600 is what he's running as far as a GPU. The 9600 is better so it's probably helping but still, a quad core will get you the best performance. I'm not saying it's absolutely necessary, but it does help. GTA IV has been programmed to take advantage of CPUs with 3 or 4 cores.