It will not help. If your video card does not have enough memory to run it, it will be far from adequate in terms of raw processing power. And if it cannot run pixel shader 3.0, there is probably not anything legit that will work.
If you really want to play GTA4, you need to get a new computer or graphics card (if its a desktop).
BTW, what computer do you have? It might not cost much to upgrade it.
i have a toshiba l500 laptop. iv already posted about a graphics card but it is intergrated so I cant replace it. actualy 1 extra question... would it be possible to add a graphics card? not replace it but add one? or send it in and get a new one intergrated on to the motherboard? if thats possible? if so how much would that cost. maybe they are wrong though because it says its bus is pci but maybr im wrong lol. what about a gta 4 downgrader? iv seen a video on youtube that downgrades the pixel shader to 2.0 but it didnt have a link for anything in the description. well whatever help you can offer would be greatly apreciated.