anas_11 :
I have all the requirements that gta 4 want gta 4 need 256 mb graphics but i have 512 mb fact is i have no graphic card will it run on my pc on low setting
This is the system requirement:
256MB NVIDIA 7900+ / 256MB ATI X1900+
Video ram doesn't make a graphics card faster.
So the fact that you can SHARE 512mb of system memory for video ram doesn't mean you have a discrete Graphics Processing Unit (GPU).
Both of the cards listed above are FAR better than onboard graphics even if the onboard graphics had 3 GB of video ram it still wouldn't be able to run that game. It's not a matter of loading stuff into video memory, it's a matter of (GPU) raw processing speed and onboard doesn't cut it.
However, most modern (inexpensive) video cards could run that game. On the other hand, I wouldn't spend a dime upgrading that rig. (It's time to save up for/consider a new desktop.)