When adjusting video settings, turning off water refraction/reflection has a big impact, especially outdoors. And helps reduce stuttering/hitching (I guess that's what you would call it).

Is the nVidia Geforce 6800 worse than the 8400GS?
It minimal required video card.

no. 6800 is the better card, only its a later generation but does not matter, in nvidia, the number you should be watching for is the 2nd number, like 6800, '8' signifies a higher shader count than the one youhave, 8400, '4' is only meant for home use or mainstream. like other cards, like for example, 8800gs is better than 9300gs, the consideration is always the 2nd number the card has, from '5' to '1' they are mainstream, from '6' to'8' they are moderate to high gaming. also another reminder for nvidia, this is the stage level of cards, rated highest to lowest type.

GTX
GT
GTS
GS
G

so these letters indicate in the end part of the nvidia video cards. G being the lowest and GTX being the highest performer. so if 6800 is in your budget then you will get more performance gain other than the 8400.

Even still the 6800 isn't going to run the game very well, it's at the very bottom of the list of supported video cards. If you want half decent performance, you should get at least an 8800 of some sort. If you shop around you can probably pick one up for very little, since it's pretty much an obsolete card these days. They probably aren't easy to find though. A 9600 or 9800 will do you as well. You don't want to go any lower than the 8000 series though, and make sure the card has at least 512 meg of VRAM.

yes i agree, because if you willing to shell some money now for temporary purposes, it's just a waste, because later on you will see another game worthwhile and time will come 8600 can't play it decently, new games and new gpus are made every quarter to say the least, so the technology trend is almost constant if you spend money on a gpu at least buy a reasonable (maybe not future proof, but reasonable) gpu.

Okay, so my 8400GS has finally came in the mail and I have finally been able to play FO3. I run it on Medium setting with water refraction and reflection off. It runs fairly smoothly, with the exception of a couple small and not annoying lags, rarely.

Low setting give me a better performance (obviously) but the graphics annoys me.

Once last question, how do you make NPC's appear from a distance, as in you can see them is the mist, without the mist.

Just go into your display settings and adjust your actor fade.

I tried that after I asked my question, didn't make a difference. I'll try again though.