BattleField bad company 2 Lag Fix

Hi , 

 I want to know how can i fix lag in battlefield bad company 2

 I am trying to change the resolution in config.ini file in documents

  the resolution is 800x600

 but when i am starting the game it runs into 800x600

  but suddenly it autochanges to actual resolution which is 1280x720

 or something like that can you kindly make a patch or downgrader as ubisoft does please 

and if you will ask my system requirements i know it does not meet even to minimum requirements

but i want  you to make a graphics downgrader 

😕mileysad: