Here are some items that I've passed on the System Requirements for GTA IV (PC)
OS : Windows 7 Home Premium 64 Bit.
And I would say that I have Failed three of them that was required in order to run the game very smoothly.
(Optimally) like it says in the game when you go into graphics settings.
But as shown in the image below, You'll see what I have passed and What I've failed and need to upgrade on.