So I installed fallout 3 on my computer and it set itself to medium settings, so I left it. It was running like crap but I wanted to get the intro thing over with so I finished it and when I left the vault my game was running perfectly. I tested it in a few places and apparently my fps drops massively whenever I'm indoors. Its a huge pain in the ass because its every indoors place, even my house and craterside supply. And in the subways the vats get so laggy its unplayable. I've tried dropping the interior shadow count and even turning shadows off, lowering my texture size, lighting etc and nothing seems to help. If I put all of my settings retardedly low it works good but I think its strange that out in the open wasteland the game runs perfectly and in tiny houses it lags up like crazy? Anyways I hope someone can help me out with this. I have the latest drivers.

Windows XP SP3
Intel Core 2 @ 2.4 Ghz
3 gb RAM
Nvidia 9400GT