Instructions
Update the drivers for your graphics card. Updated drivers will often have enhancements that increase performance. By downloading and installing the latest drivers, you will have the fastest possible software running your graphics card.
Exit all running programs and applications. The computer has to split its resources to manage each running program and some programs can be fairly resource-intensive, taking away processing power that could otherwise be used to run the game. Anti-virus programs especially can cause a severe loss in framerate if they are running in the background. Disable anti-virus scanners and exit out of all other running programs and windows before starting the game.
Lower the video resolution through the game's settings menu. Higher resolutions demand more power from the computer in order to display smoothly. Playing the game at a lower resolution will almost always produce a boost in framerate, sometimes dramatically.
Reduce graphical distances through the settings menu for increased performance. The higher the view and detail distance is set, the more information the graphics card will have to process. Lowering these settings limits the workload on the graphics card and can improve framerate.
Lower vehicle and shadow density in the settings menu. The shadow density setting controls the number of independent shadows created by exterior light sources. Lowering the density will reduce the number of shadows displayed and improve performance. The same goes with the vehicle density settings. Reducing the number of vehicles generated for city traffic will not affect the difficulty of the game but it will make it easier for it to run smoothly.
Create a new file called "Commandline.txt" located in the main "Grand Theft Auto IV" folder. Open the file with a text editor and add on separate lines:
--norestriction
--nomemrestrict
--availablevidmem 1
--percentvidmem 100
This will remove memory restrictions and allocate all available video memory to the game. You can also add "--minspecaudio" to force the game to use the lowest possible audio quality, freeing up additional resources.