Heya bldr,
First off, Welcome to SimV!
With your system specs you should be running FS 2004 with max settings without a sweat. The first question that I would ask is --> Was there ever a time that FS 2004 ran fine with max settings on your PC? Or has it been this choppy since the original install?
If the choppy graphics are a recent thing then perhaps you installed a scenery package that doesn't agree with your FS 2004 installation. I would go into the settings menu and bring up the Add-On Scenery Library, uncheck all 3rd party add-ons, then restart the game. If everything works fine then it's a process of elimination to determine which scenery add-on is causing the issue.
The next thing that I would do is to investigate the NVidia drivers themselves. I've found out in my long experience that not all graphics drivers are equal, meaning that the latest driver update is not necessarily the best. I always avoid those NVidia "Beta" drivers and those NVidia drivers that aren't WHQL Certified. I have always used the NVidia 7.2.1.3 driver (05/07/2005) because it renders the best overall graphics. You can find this driver on the
www.guru3d.com webpage. Try it and see if it works better.
Another little trick is to turn off AntiAliasing in FS 2004 by going into Options --> Settings --> Display --> Hardware and unchecking the AntiAliasing box.
Next click on your NVidia Control Panel (Found in the NVidia MC Tray Icon next to your XP timeclock). Under Performance and Quality Settings Turn on AntiAliasing in the NVidia settings and use either the 2X, 2XQ, or 4X AntiAlias Settings. Whichever gives you the best graphics with the best performance (I have my Nvidia 6800 set for 4X). Again in the NVidia MC Tray under Performance and Quality Settings bring up Anisotropic Filtering and set it to