You cant play the game with the minimum requirements cause they are false.
*cough* I have an Pentium 4 HT 3 GHZ and an 512 MB NVIDIA 8400 GS.
The Pentium 4 processor does not meet with the minimum requerments, but the game is working perfectly for me.
If you want to have your game run smoothly, just set everything on the lowest settings (Shadow settings on 3) and choose the lowest resolution as possible with the highest hertz which your monitor support. Then GTA IV looks an little less detailed then it normaly should be, but you are able to play the game without lagg and any other problem.

Or maby just buy the game. :rules: