My system seems to have almost the same graphics capabilities after I upgraded my VGA (BFG 9800Gt 1gb-----EVGA GTX 460 1gb). I haven't noticed almost any difference in this game and others that are much more needy like Crysis. My guess is that my cpu is bottlenecking my system, but I am not that computer savvy. Help please?

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OS: Win 7 Pro 64-bit

If you need other info just ask.

Your processor is not bottlenecking that GPU.

It be nice to know what settings this system is running the game at. Resolution as well.

Also, after you made the change of the graphics card, did you delete the .ini file in your My Documents folder? You can find the .ini file in your My Documents/My Games/Fallout3 folder...it is the configuration file named FALLOUT. Delete it, then refire up the game so a new one gets generated that will re-detect your hardware config.

Didn't change anything. And that wouldn't explain Crisis lagging at max as well. My gc should be able to do everything at max.

Hard to tell, looking at available Benchmarks you should see some improvement.
It's possible that there are some software or driver issues.

You could have a look if there are newer drivers available.
Maybe you have a lot of unnecessary background processes running. Many pc's with preinstalled OS also come with a lot of bloatware.

You can also post your DXDiag.

9800 GT already runs the game very well, I have a 9800GT OCed and have AA at 8 and AF at 12 and don't notice any slowdown even in firefights. This is at 1920x1280.

If anything you should be capable of bumping all graphic settings to the max making it look much better.

When you say Performance what exactly do you mean? Post some framerates.
You also need to post a dxdiag as someone suggested.

Setting performance mode in the nvidia driver to max performance can help with lag issues.

I'll post framerates and dxdiag soon. Sorry my Internet is in and out on my gaming PC, mostly out. The all around performance in this game and others like borderlands, crysis, etc are not really improved. Performance meaning frame rates and higher settings in shadows, anti aliasing, etc. I made a big leap in video cards yet the framerates seem to be the same...
It's not bloat. My PC is custom built with hardly anything running in the background.

Sounds like a software issue to me. I would start by uninstalling the display drivers and installing the latest Nvidia drivers.