It can be a number of things. How many things to you have starting up when your pc boots. Check you startup tab under your msconfig. Also, the longer bf3 plays, the hotter your gpu can get. On your harddrive, you can do a scandisk and check for errors. This should also check to see if you have any bad cluster on your disk. Also with bf3 running under a ie. Check your your history and disk cleanup. Your cache could be overloading. Do some of the others things mentioned here like memory test and so and then get back to us. Pretty sure with all the pc smarts guys and gals here. We can work it down to the problem.