You can't, end of story (and I know it's not what you want to hear). GTA IV runs like *** on the PC, even on high end systems. Your computer has a 250 Watt power supply and a motherboard with a PCIe x16 slot which means you can't even put a decent gpu in it. Not only that, but I'm not sure you have the processor nor the RAM for it.
I have a Dell Inspiron 530s and I want to buy a video/graphics car
for it to run GTA IV. Which, if any, should I buy for it?
is this your pc? http://www.dell.com/us/dfh/p/inspiron-530s/pd
looks like it has only 250 w power supply. no high end gfx cards even most of entry level cards will run using psu with that wattage. for example, to run an entry level card like radeon hd 6670, amd recommends a typical 450 w psu.
gta iv is a poorly coded console port that is a resource hog. even high end pcs have trouble running it.
you'll need a whole new pc with a quad coree cpu, 8-16 gb ddr3 ram, radeon hd 5770 or higher gfx card with at least 1 gb gddr5 vram with 500+ watt psu (80+ rated preferred).
here's a link you can consult: http://www.tomshardware.com/forum/113964-13-requirement...