Hi i bought fallout 3 (I know new vegas is out) at the weekend and although my laptop is actually a little bellow the requirements 2.1ghz 4gb ram, it seems to run fine on low and medium until you go into a building and it gets Very choppy, for example it runs like normal in the wasteland or megaton but if you go into a building or rivet city then it starts to get very jittery, why does this happen does anybody know how to fix it? Thanks in advance, and I don't have any viruses.