Make sure you do not have any mods installed, if you do, then you will have to delete them and downgrade. You probably have V2 and that doesn't allow for the gta3.img to be bigger than it is programmed to be, therefore it will crash. If that isn't the case, then update your drivers, check your system requirements like recommended by *JAJ*. On which part does it stop? I had a problem like this, mine used to stop on the nVidia splash screen. All I had to do was keep on clicking it, and then it would work.