I am able to play GTA-4 on SONY VAIO VPCEH26 (i3, nvidia 410m 512mb, 4gb ram). It is running satisfactorily. But the game is getting stuck very often on Hp pavillion g6 (i5, ATI radeon HD 6470 - 1gb , 4GB ram).
On my HP, I have tried my best for reducing the load on CPU by reducing all the services. I have formatted my lappy and then installed gta4 alone. same game is running fine on sony lap with lot many applications,