hi.i have pc core i5 with 600 psu and my gpu is gtx 660 2gb.3 days ago it was good.when i start a game it starts and fans works like a thunder and performence was good.but now when i start any game it is still so quite.not working fast and every game display lags.i update drivers.install new windows too.but not working.i play nfs rivals high settings but it is givin lag on low settings now.farcry 4 was running smoothly on medium but now its laging on low settings.gpu is working but not get accelrated when game starts.plz tell me solution