The file is called ControlMap.dat and it resides (by default in):
~installdrive~\Users\~username~\AppData\Local\Rockstar Games\GTA IV\savegames\~user_xxxxxxxxxxxxxxxx~\
Where ~installdrive~ is the volume on which the game is installed, ~username~ is your currently logged on user from which you play, and ~user_xxxxx~ is a uniquely generated xlive save directory.
However, if you are thinking of opening this file in a text editor to quickly change something, you won't have any luck. The file isn't plain text. You'll see what I mean when you open it this way.
~PhoenixCH
Lol i was thinking of opening it with a text editor but of course that would be too easy. So can it be open with something else.
The trouble is i try to change the keyboard mapping in the options the but the keyboard settings go back to the default settings when i go into the game.
Are you properly applying the settings after re-mapping the controls? There should be a button to confirm near the bottom right of the screen somewhere. Spacebar should also do the same thing (it does with the other settings such as graphics).
No it doesn't look like i am doing it correctly but i have it working now. So i don't know what i did wrong.