I stopped playing Fallout 3 due to the crashes, same with Oblivion, never came back to them, and I've been doing mods for both. Fortunately (for sanity's sake) I was spending more time in the Construction Set and the G.E.C.K. than in the actual game playing it, still, the crashes turned me off entirely after a year or so with Oblivion, and after a year as well with Fallout 3, a real shame because I've always liked those games for what they were excluding their stability problems.
I spent countless hours trying to tweak both of them to no avail, sure I was able to stabilize them "more", allowing me to play for one or two hours at times, but I was never ultimately able to play a single (not a single one) play session without at least one crash. But, anyway, I've discussed this to death back then and I won't get too much into this, it'd be futile, in the end all I can say is good luck, you'll need it. Just check the official forums and look at the PC and Console versions of the technical support sections, you'll be able to comfort yourself in knowing that you're not alone in that boat, believe me (yes, even the Console versions crash, so just imagine with PCs and the numberless variations of hardware and software combinations).