Remove all options except "Transform and Lighting" in FS2004 under the Options> Settings>Display and Hardware tab. Set your mip-map quality to 4, set hardware lights to 8.
Right click on desktop and select Properties menu.
Click the Settings tab & click the Advanced button down the bottom.
Click the tab that lists your vid card (6800GT in my case). Sad
This is your Nvid controls. Go to the section called Performance & Quality Settings. In the Application Profiles box, select fs9.exe and FS2004:ACOF from the Application and Active Profiles boxes respectively.
Now click the Modify Profile... button and select "Modify" from the two choices.
Now you can tweak the Nvidia settings...
Make sure the View: Advanced Settings is selected. From the available selections, tick the boxes and set them up as per below:
X Antialiasing settings 2xQ/4x (whichever is best for you)
X Anisotropic filtering - OFF
X Image settings - Quality
Color profile (leave blank)
X Vertical sync - ON
X Force mipmaps - Trilinear
X Conformant texture clamp - ON
X Extension limit - OFF
X Hardware Acceleration - Single display mode
X Trilinear optimisation - ON
X Anisotropic mip filter optimisation - ON
X Anisotropic sample optimisation - ON
Transparency antialiasing - OFF (don't tick the box)
X Triple buffering - ON
X Negative LOD bias - CLAMP
Now click OK and the new settings should be saved and activate when you start FS2004.
These are not fool-proof settings, but they upped my FPS in FS2004 considerably and let me run things like clouds without too much of a frame hit. But in my 11 years of experience with Flight sim, it's graphics options as pertaining to hardware stink. Let the graphics drivers handle it instead.
There are also many tweaks for this software on www.flightsim.com.
Adjust these settings to your liking, but these seem to be a good base for most cards. Your card may have more options than mine
Hope this helps!!!