finally, I've bought a new Notebook
it's a Lenovo Ideapad Y700 - i7 + GTX960M
However, this is the problem:
GTA IV doesn't seems to recognize the video card, the game always seems not to use the GTX;
looks like the game starts with that intel graphics chip only.
I already created a commandline and wrote availablevidmem and similar stuff into it;
also told the game to use the GTX by using the nVidia control panel.
I'm using the Steam version;
BTW; this happens with EFLC as well