GTA IV Lag

I installed GTA Iv on my pc.
I have:
Core i5
4GB Ram
Win 7
ATI Radeon HD 4350 1GB Graphics card.
GTA IV with patch 1.7
All working well.
But While on driving there is a little lag continuously occurring.
I tried all settings from High to Low.
But failed.
Help me to slove.
Answer #1
maybe because of the graphics card. gta4 is a monster resource hog.
Answer #2
It sounds like the hdd. If i am not mistaken gta4 loads the world as you go.
Answer #3
Not surprising for a badly-coded game. And GTA IV is a CPU-intensive game.