create a txt file and name it commandline.
open up the file and replace this in it exactly as it is copy and paste
-norestrictions
-nomemrestrict
-percentvidmem 100
-availablevidmem 4.0
once you have copy/pasted in these,put the txt file in rockstar/grand theft auto folder and run the game
If you're using the steam version, you need to start GTA with a shortcut pointing to the GTA4 Launcher to get the commandlione.txt file to work. Don't start it from Steam itself or this won't work.
Cavallino :
For fps use Fraps - www.fraps.com