Windows 7 - Constant CTD's and freezes when playing fallout 3

Hi, i have been spending alot of time on this problem, and everything does not seem to work. i have windows 7 home premium 64-bit, with a AMD Phenom II 945 Quad-Core processor. my graphics card is an ATI Radeon HD 5450, with an intergrated sound card and 8gb ddr3 memory. generaly, a problem arises within 20 mins of gameplay (does not matter if im outside or inside), and presents itself either as a crash-to-desktop or a freeze. also i am not playing with any mods or DLC's or with New Vegas i have tried many fixes; i have set the INI to use only 2 (then 1 processor), disabled all autosaves, downloaded/installed the d3d9 file, changed windows color scheme to "basic", i have updated all my video card drivers, i am not aware of any codecs being used on my system (did a file search, came up w/ nothing), running as administrator, allowed all premissions (its even installed in my documents, NOT program files), and even now i still have this problem. however, i can also play Oblivion w/ about 300 mods and i can play pretty comfortably. on top of that (even though i dont have the most recent games) Fallout 3 is the only problem.

if anybody has any suggestions at all, that would be great from what ive played, Fallout 3 is very fun, and hope i can actually play it
thank you

This is a total shot in the dark here, but have you tried limiting the amount of RAM the game uses? I know it doesn't sound logical but if you know how to do that, to only let the game use about 4GB that might help.

I think it's safe to assume it ISN'T your CPU or GPU, nor a Windows/malware etc. issue as you've seemed to rule those out already.

In any case, you shouldn't be having problems with that game on your rig... I only encounter the random CTD every so often (and I'm finding it's typical on almost all "console port" PC games) on Fallout 3 (NOT New Vegas, yet) with my Notebook rig (see specs)...

I too can play Oblivion, even Skyrim (which seems ironically enough to play better and easier on my system than Oblivion) without problems - other than infrequent CTD's.

Good luck.

EDIT: The other thing I would try is messing around with the game's settings, both graphics and the rest. See if it still presents. I notice my Fallout 3 won't even launch if I don't have the Resolution set to 1920x1080!

alright well when i was playing around w/ the game settings, i noticed it was using a "Nvidia GeForce 7800" or somthing like that, but whats weird is i dont even HAVE an nvidia card im wondering could this be the problem?

I'm running a Dell E5520 laptop with integrated graphics.
What I found to do the trick, oddly enough, is to disable Hyperthreading in BIOS setup.
Looked thru a bunch of forums to find this solution.
The only issue I found was that the cooling fan ran all the time to decipate the heat, but other than that, the game ran flawlessly. I played about 4 hours straight with no issues or freezes.
Of course, I enabled the Hyperthreading after I quite the game.