Can only use low profile graphics cards due the small tower.
And also he said that my power supply was only 220 Watts which is not good enough. And low profile video cards all usually need 300 watts power supply. So I'm basically helpess right now. I got no idea what to do. I don't want to sell the PC and buy a new one, parents wouldn't let me... but yea he told me to go on newegg.ca which is a Canadian PC hardware site and I found this.
Those would be beginning gaming cards that could do low setting low resolution. MW3 would be little difficult for it. A better plan would be saving up for a tower case and move your components over with a bigger PSU and a gaming card!