lol theres no way to do it on mw2 (unless youd like to play with stickmen) my best bet is to get a better graphics card, at least 512 mb( then if that dosent really fit your need you can overclock its bus speed [NVIDIA is the gpu of my choice btw]) check your video cards pc requirements (that is if your actually going to get one) and make sure your power supply can handle the little devil (if it cant then your gonna need to invest in a bit more money and get yourself a beefy power supply). BUT if you cant handle pimping out your pc then ill tell you right now YOU ARE NOT WORTHY OF HARDCORE PC GAMING.
BTW the people usually not worthy are just your typical average console NOOBLETS