thanks a lot for answering my question. but i have one more question for you. there is a problem with my gpu. i have tried everything to fix it but nothing works. when i play and low spec games the gpu works fine. but when i play games like battlefield 3 or arma 3 the gpu stops working and the driver crashes. i used DDU and installed the latest driver from scratch but nothing works. i also changed my laptops OS. but still no success.and finally i removed the gpu cleaned it put new thermal paste. but still the problem is there.