|Let me know what specs does your laptop have. Mine are on top of this thread. I'll give you the commands I added to mine, but they may have to be different for your laptop.|
On the install folder of your GTA IV, create a txt file named commandline.txt, it should be filled with the following text:
And FYI, -availablevidmem 2.500 is the command that allocates the RAM memory for video memory, you can change it a few numbers down or up depending on your needs. Try it out to find the right one for your laptop, as all depends on how much RAM you're packing.