I have a Compaq Presario CQ57. It as a AMD Radeon HD 6520. I found a better graphics card for it (AMD Radeon HD 7970M for $450) and was wondering if i can install that into it. If not please tell me why. and if i cant, can someone please help me find a graphics card for it under $600 that can play Arma 2: Dayz and Battlefield 3. I also dont know alot about computers. Someone also told me that it would need a new motherboard, but i dont know what that is. Any help is appreciated.