Fallout 3 FPS Problems....

[foxtrot08]

I'm pretty frustrated trying to find out why fallout 3 is fps lagging. I have a Gateway LX6810-01, it has 8GB Ram, Q8200 Processor, and Nvidia GT-120. With that, i selected high quality settings as my default. I played perfectly well and fine.
I stopped playing after a while and decided to buy and replace the GT-120 with a Geforce Gtx-260.

I wanted to play again, so i started up fallout 3 again with the same settings. I was playing one of the DLC's : Operation Anchorage, and every time any npc would shoot their guns, my fps just insanely drops low...Why? I don't understand. Lol, and its weird. Can anyone help me?

Edit:

-Random fps lag.
-when i go into VATS, it lag
-On LOW SETTINGS, it fps lags.

 

[Crono]

You have latest drivers, I assume? First thing I would try is upgrading driver, and if that doesn't work, rolling back to a previous driver.

 

[WaitingForNehalem]

Did you reinstall the drivers? BTW, if you have 185, rollback to 182. 185 has given me problems.

 

[foxtrot08]

I already tried updating to the latest settings. Is it okay if i uninstalled the display driver and then install the drivers again?

Edit:

The version before i updated to the latest version was doing the same thing.