Try right clicking on computer and manage, when the window pops up go on Services and Applications, then on services. Then you should get a long list of your computers services, go down to Windows Event Collector and Windows Event Log, right click on both of them go on properties and change startup type to disabled and then ok.
Restart your computer and startup GTA IV, it should give you an extra 10 FPS and when your done go back and switch the startup type to what you had before. This actually helps because sometimes when you press a certain key it causes the game to slow down and sometimes crash. Hope it works! Good Luck!