There are plenty of websites that have already discussed this subject of this 5 year old game.
Check "GTA4 hardware requirements"
i want to play gta 4 at my desktop. it needs high requirement
i inserted nvidia 9800 graphics card but still its not working. i ant play smoothly. please help me someone what sort of graphics card i will need for this

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic