BF3 Fps drops

So i built my brother a mid range gaming pc a few weeks ago and it would run bf3 on ultra and 2xaa but now it just seems to want to give up on keeping stable frame rates. i have reinstalled drivers antivirus sofware put it some code that stopped it moderatly but now every so often it just goes from 40-60 frames on 64 man caspian border and just randomly drop down to 5-10 frames for about a second. I ran msi afterburner and his gpu is only running at 50-70% while playing bf3.

i3 3220

gtx660 gigabyte oc 

8gb gskill ripjaws



Any help?

Thanks in advance.

Uninstall the newest drivers from nvidia and find the ones that worked best for you because with my card I could barley playgmod 670" because of the new driver update 

whats the vram on the card? its possible in 64 man servers that a 1 gig card coupd peak on one of the bigger maps like that