After playing FNV I decided to play FO3 again. I have the same hardware I did when it was first released in 2008, but W7 64 instead of Vista 64.

FNV ran fine, in fact with all options as high as they'd go in 1280x960 it wouldn't really spin up the fan on my GPU. Now, FO3 seems to push the fan speed up as high as it'd go.

The framerate is actually just fine, but what's making it impossible to play is constant lag/freezing, usually just while outdoors. Not the normal little loading stutters that we all expect from these games, but where it'll actually freeze the display for several seconds (or longer) at a time.

As an experiment I tried using NMC's texture packs. The Full pack made it much, much worse outside - so bad that it took me a long time just to get into the esc menu to quit the game. Still just fine in interior areas. I removed that and tried installing the Lite pack, which to my understanding actually uses lower resolution textures than the standard game. It was still pretty bad - sometimes it'd be ok for a few minutes after going outside but would quickly turn into a slideshow. I reverted to vanilla FO3 again and it still did it.

After changing the game from Large textures to Medium it seems ok, aside from looking really bad. This is frustrating because, like I said, I actually don't have any FPS issues - it's this crippling freezing outside that's making it unplayable. I know that I played through the game with Large textures before, so my guess is that it's somehow related either to nvidia drivers or something being different between W7 and Vista. The last set of drivers (released Oct. 25th) do mention "performance improvements" for FO3. I've also tried various .ini tweaks without any luck.

Any help is appreciated!

Operating System: Windows 7 Ultimate 64-bit (6.1, Build 7600) (7600.win7_gdr.100618-1621)
Language: English (Regional Setting: English)
System Manufacturer: Gigabyte Technology Co., Ltd.
System Model: EP35-DS3L
BIOS: Award Modular BIOS v6.00PG
Processor: Intel® Pentium® Dual CPU E2180 @ 2.00GHz (2 CPUs), ~2.0GHz
Memory: 2048MB RAM
Available OS Memory: 2046MB RAM
Page File: 1789MB used, 2303MB available
DirectX Version: DirectX 11

Card name: NVIDIA GeForce 8800 GT
Manufacturer: NVIDIA
Chip type: GeForce 8800 GT
DAC type: Integrated RAMDAC
Device Key: Enum\PCI\VEN_10DE&DEV_0611&SUBSYS_053C196E&REV_A2
Display Memory: 1266 MB
Dedicated Memory: 499 MB
Shared Memory: 767 MB
Current Mode: 1280 x 960 (32 bit) (75Hz)
Driver Name: nvd3dumx.dll,nvwgf2umx.dll,nvwgf2umx.dll,nvd3dum,nvwgf2um,nvwgf2um
Driver File Version: 8.17.0012.6099 (English)
Driver Version: 8.17.12.6099

Join us on the Win 7 64 boat.

I was thinking it was 400+ series Geforce cards +Win 7 64 but since you're still running an 8800 GT that would narrow it down to a Win 7 64 Bit problem.

I have Win 7 64-Bit and an Nvidia card but no problems.

You have all options on max you say? Could be chewing through your vram. Try a test run on the game's medium setting with antialiasing off and get back to me.

I've always had AA off, but I did lower the settings to "medium".

I tried it on Medium settings for a while, with Large textures, and it did take a lot longer to start lagging, and then wasn't quite as bad when it did (still unplayable but more like a really fast slideshow instead of a slow one). Vram sounds like a good explanation, but what can I do about it?